Liquid crystal display films

ABSTRACT

The present invention relates to a display film that may be transferred by lamination or otherwise onto a substrate. The display film is formed of a stack of layers that can include different types, arrangements, and functionality within the stack depending upon factors including the characteristics of the substrate (e.g., upper or lower, transparent or opaque, substrates) and addressing of the display (e.g., active or passive matrix, electrical or optical addressing). The layers of the stacked display film include one or more electrode layers and one or more liquid crystal layers and, in addition, may include various combinations of an adhesive layer, preparation layer, casting layer, light absorbing layer, insulation layers, and protective layers. The liquid crystal layer can include cholesteric or other liquid crystal material. The liquid crystal layer can be a dispersion of liquid crystal in a polymer matrix formed by a variety of techniques. The display film may interact with components mounted on or laminated to the substrate, including a solar cell, active matrix backplane and electrodes. The display film may be mounted onto flexible or drapable substrates such as fabric and can itself be drapable. Thus, the invention offers substantial flexibility in fabrication and design that has not been previously possible in the display industry.

I. RELATED APPLICATIONS

The present application is a 371 of U.S. Patent Application No.PCT/US2005/003144, which was published in English on Aug. 11, 2005,which is a continuation of U.S. patent application Ser. No. 11/006,100,filed Dec. 7, 2004; Ser. No. 10/782,461, filed Feb. 19, 2004; and claimsthe benefit of co-pending U.S. provisional patent applications Ser. No.60/539,873, filed Jan. 28, 2004; and 60/598,163, filed Aug. 2, 2004, allof which are incorporated herein by reference in their entireties.

II. GOVERNMENT SUPPORT

This application was made in part with United States Government supportunder cooperative agreement No. DAAB 07-03-C-J406 awarded by theDepartment of Defense. The government may have certain rights in thisinvention.

III. FIELD OF THE INVENTION

The present invention relates to the field of liquid crystal displaysand, in particular, to the fabrication of such displays.

IV. BACKGROUND OF THE INVENTION

A revolution in the information display technology began in the early1970s with the invention of the liquid crystal display (LCD). Becausethe LCD is a flat-panel display of light weight and low power whichprovides a visual read out that conforms to the small size, weight andbattery demands of a handheld electronic device, this display technologyenabled a new broad class of handheld and other portable products.Commercially, the LCD first appeared in volume as a digital readout onwrist watches, then on instruments and, later, enabled the laptopcomputer, personal data assistant and many other digital devices. TodayLCD technology is even replacing cathode ray tubes in televisions andPCs.

Nearly every commercial LCD display manufactured and sold today is onglass substrates. Glass offers many features suitable for themanufacture of LCDs. It can be processed at high temperatures, it isrigid and suitably rugged for batch processing methods used in highvolume manufacturing, its surface can be made very smooth and uniformover large areas and it has desirable optical properties such as hightransparency. There are many applications, however, where glass is farfrom being the ideal substrate material. Glass substrates cannot be madevery flexible and are not very rugged, being unsuitable for webmanufacturing and subject to easy breakage. As a result there is a largeworldwide effort to develop displays on more flexible and ruggedsubstrates that cannot only conform to three-dimensional configurationsbut which can also be repeatedly flexed. A display is desired that hasthe flexibility of a thin plastic sheet, paper or fabric, so that it canbe draped, rolled up or folded like paper or cloth. This would not onlymake the display more portable and easier to carry, it would expand itspotential applications well beyond those of the typical flat panelinformation displays known today: A display worn on the sleeve; the backof a bicyclists coat that shows changing direction signals; textile thatchanges its color or design are but a few examples.

While the ability of an electrically addressable liquid crystal displayto be flexible and deform like cloth or paper would be advantageous forany LCD technology, it is especially advantageous in applications suitedto cholesteric liquid crystal displays. Cholesteric displays can be madehighly reflective such that they can be seen in bright daylight or adimly lit room without the aid of a heavy and power consuming backlight.Since cholesteric liquid crystals can be made to be bistable theyrequire power only when being addressed, further adding to the powersavings associated with such displays. Cholesteric liquid crystallinematerials are unique in their optical and electro-optical features. Ofprincipal significance, they can be tailored to Bragg reflect light at apre-selected wavelength and bandwidth. This feature comes about becausethese materials posses a helical structure in which the liquid crystal(LC) director twists around a helical axis. The distance over which thedirector rotates 360° is referred to as the pitch and is denoted by P.The reflection band of a cholesteric liquid crystal is centered at thewavelength, λ_(o)=0.5(n_(e)+no)P and has the bandwidth, Δλ=(n_(e)−no)Pwhich is usually about 100 nm where ne and no are the extra-ordinary andordinary refractive indices of the LC, respectively. The reflected lightis circularly polarized with the same handedness as the helicalstructure of the LC. If the incident light is not polarized, it will bedecomposed into two circularly polarized components with oppositehandedness and one of the components reflected. The cholesteric materialcan be electrically switched to either one of two stable textures,planar or focal conic, or to a homeotropically aligned state if asuitably high electric field is maintained. In the planar texture thehelical axis is oriented perpendicular to the substrate to Bragg reflectlight in a selected wavelength band whereas in the focal conic textureit is oriented, on the average, parallel to the substrate so that thematerial is transparent to all wavelengths except for weak lightscattering, negligible on an adjacent dark background. These bistablestructures can be electronically switched between each other at rapidrates on the order of milliseconds. Gray scale is also available in thatonly a portion of a pixel can be switched to the reflective statethereby controlling the reflective intensity.

The bistable cholesteric reflective display technology was introduced inthe early 1990's as a low power, sunlight readable technology intendedprimarily for use on handheld devices. Such portable devices demand longbattery lifetimes requiring the display to consume very little power.Cholesteric displays are ideal for this application as the bistabilityfeature avoids the need for refreshing power and high reflectivityavoids the need for power-consuming backlights. These combined featurescan extend battery life times from hours to months over displays that donot have these features. Reflective displays are also easily read invery bright sunlight where backlit displays are ineffective. Because ofthe high reflective brightness of a cholesteric display and itsexceptional contrast, a cholesteric display can be easily read in adimly lit room. The wide view angle offered by a cholesteric displayallows several persons to see the display image at the same time fromdifferent positions. In the case of cholesteric materials possessingpositive dielectric anisotropy, modes of operation other than a bistablemode are possible by applying a field to untwist the cholestericmaterial into a transparent, homeotropic texture. Quick removal of thefield transforms the material into the reflective planar texture. Themore fundamental aspects of such modern cholesteric displays aredisclosed in, for example, U.S. Pat. Nos. 5,437,811 and 5,453,863,incorporated herein by reference.

Bistable cholesteric liquid crystal displays have several importantelectronic drive features that other bistable reflective technologies donot. Of extreme importance for addressing a matrix display of manypixels is the characteristic of a voltage threshold. A threshold voltageis essential for multiplexing a row/column matrix without the need of anexpensive active matrix (transistor at each pixel). Bistability with avoltage threshold allows very high-resolution displays to be producedwith low-cost passive matrix technology.

In addition to bistable cholesteric displays with liquid crystallinematerials having a positive dielectric anisotropy, it is possible tofabricate a cholesteric display with liquid crystalline materials havinga negative dielectric anisotropy as, for example, described in the U.S.Pat. No. 3,680,950 to Haas et al., or U.S. Pat. No. 5,200,845 to Crookeret al., incorporated herein by reference. These “negative materials”like the “positive” materials are chiral nematic liquid crystals thatare prepared from nematic materials that have been twisted into ahelical molecular arrangement by the addition of chiral compound orcollection of chiral compounds. The negative and positive materials areprepared from nematic liquid crystals with either a negative or positivedielectric anisotropy respectively.

Negative type cholesteric displays can operate in a bistable mode wherethe material is switched into the stable planar (e.g., color reflective)texture with an AC pulse or into the stable focal conic (e.g.,transparent) texture with a DC pulse as described by U.S. Pat. No.3,680,950. There are other modes of operation such as has been disclosedby Crooker where a droplet dispersion of negative cholesteric materialsis switched into the planar, color reflective texture with an appliedelectric field, but relaxes back into a transparent texture when thefield is removed.

Some cholesteric materials possess a dielectric anisotropy that can benegative under an applied electric field of one frequency but positiveat another frequency. This feature can be used to drive a bistabledisplay using a dual frequency drive scheme as described in U.S. Pat.No. 6,320,563, incorporated herein by reference.

Another important feature of cholesteric materials is that the layersreflecting red, green, and blue (RGB) colors as well as IR night visioncan be stacked (layered) on top of each other without opticallyinterfering with each other. This makes maximum use of the displaysurface for reflection and hence brightness. This feature is not held bytraditional displays where the display is broken into pixels ofdifferent colors and only one third of the incident light is reflected.Using all available light is important for observing a reflectivedisplay in a dimly lit room without a backlight. Gray scale capabilityallows stacked RGB, high-resolution displays with full-color capabilitywhere as many as 4096 colors have been demonstrated. Because acholesteric display cell does not require polarizers, low costbirefringent plastic substrates such a PET can be used. Other features,such as wide viewing-angles and wide operating temperature ranges aswell as fast response times make the cholesteric bistable reflectivetechnology, the technology of choice for many low power applications.

Cholesteric liquid crystals are particularly well suited for flexiblesubstrates. Such cholesteric displays have been reported by Minolta Co.Ltd. and by Kent Displays, Inc. involving two plastic substrates filledwith cholesteric liquid crystal materials (Society for InformationDisplay Proceedings, 1998, pp 897-900 and 51-54, respectively). Whilethe substrates themselves are flexible, the assembled displays are muchless flexible because of the lamination of two substrates together.Minolta has developed procedures for manufacturing flexible displayswith two substrates as seen in U.S. Pat. No. 6,459,467.

Greater flexibility can be achieved if only one substrate is used andthe display materials are coated or printed on the substrate.Cholesteric liquid crystals are made suitable for standard coating andprinting techniques by forming them into polymer droplet dispersions. Asdroplet dispersions, the materials are made insensitive to pressure andshear such that an image on a bistable cholesteric display is notreadily erased by flexing the substrate. Recently, Stephenson et al., atKodak fabricated flexible bistable reflective displays with polymerdispersions of cholesteric liquid crystals on a single transparentplastic substrate using photographic methods (U.S. Published ApplicationNo. US 2003/0202136 A1 and U.S. Pat. No. 6,788,362 B2). This processinvolves a sequence of depositions on transparent polyester plasticwhereby the end product is a display where the images are viewed throughthe substrate. Such a process requires substrate materials that aretransparent such as a clear plastic sheet.

In view of the foregoing, it is desirable to provide a reflectivedisplay that does not require a transparent substrate, making availablea broader range of substrate materials such as fabrics made of fibersthat can be deformed such as by bending, rolling, draping or folding.These added features offer many advantages and open up many new displayapplications. Use of flexible and drapable substrates can bring to themarket place new displays that have the physical deformability of fabricso that they can be an integral part of clothing and have the feel andappearance of cloth because they can be draped and folded.

V. DISCLOSURE OF THE INVENTION

The present invention features a novel concept in liquid crystal displaytechnology: a display that is a manufactured film. The invention is adisplay film that is fabricated, lifted off a release liner and thentransferred to any desired substrate. The display film may be fabricatedby applying a plurality of layers in sequence to include all displaycomponents or can be fabricated with some components and later laminatedtogether to complete the display device.

A. Display Film

1. General

The display includes a plurality of coated, printed or laminated layersthat form a film that has the elements of a reflective display includingliquid crystal material, transparent conducting electrodes, insulationlayers to prevent electrical shorts, and protective layers for providingruggedness. All of the layers are stacked together in a veneered orlaminated film forming the framework of the display. The layers are eachcast, in sequence or simultaneously, on a release surface (e.g., arelease liner), cured or dried and then lifted off of the release liner.This forms a lift-off display element itself without any substrate.Other components may be added such as drive circuitry and connectionsthereto. The display film may be transferred to some desired substratein which case it is referred to as a transfer display film. The displayfilm can be transferred onto any desired surface, rough or otherwise,that can contain the interconnecting electrodes to the drivingcircuitry. The interconnects can be added before or after lamination.Once the display film is connected to electrical drive circuitry it canbe electronically updated to produce images from the display.

A substrate as defined herein is a structure that supports components ofa liquid crystal display including a liquid crystal layer that iselectrically addressed to produce images. The substrate need not berigid but can be flexible or drapable as disclosed in U.S. applicationSer. No. 11/006,100, filed Dec. 7, 2004, which are incorporated hereinby reference in their entirety. Glass, metal, polymer, paper and fabricor textile can all be used as substrate materials. The substrate is agenerally thin layer, but is often significantly thicker than othercomponents of the display. As defined herein and consistent with U.S.Pat. No. 6,788,362 owned by Kodak, a substrate is a layer that has athickness of at least 20 microns and, in particular, at least 50microns. Substrates of liquid crystal displays on the market today canhave a thickness of 100 microns or more and substrates such as fabricscan be substantially thicker exceeding 1000 microns. The substrate canbe formed of or have various components attached to it such aselectrodes, an active matrix backplane, solar cell, photovoltaic deviceand the like. The present invention is usable in connection withdisplays employing one, two, or more substrates. A casting layer asdefined herein is a film layer of the inventive multilayer film appliedon or near the release liner on which other film layers of the displaymay be printed or coated. The invention may employ various layers thatfunction as casting layers including a preparation layer, electrodelayer, adhesive layer, planarization layer, liquid crystal layer,isolation layer and combinations thereof. The multifunctionality of thelayers of the inventive display film is discussed in more detail below.

In some cases, it may be desirable for the display film to only containsome of the elements of the display for transfer onto a substrate thatalready contains other display elements. For example, the transferdisplay film may contain one layer of printed electrodes, a liquidcrystal droplet dispersion layer, and a protective layer that is liftedoff of a release liner then transferred onto a substrate having theother conducting electrodes of a passive matrix or an active backplane.

The display film can be electrically addressed by adding suitableelectrical interconnects during or after lamination or after removalfrom the release surface. The electrical interconnects allow driveelectronics to be connected to the electrodes of the display film. Thedisplay film may be laminated onto a substrate already containingelectrodes such as the column or row electrodes of a passive matrix, thepixel electrodes of an active matrix backplane or drive electronics.

While the invention will be described herein primarily in conjunctionwith the preferred use of cholesteric liquid crystals, any liquidcrystal material that can be adapted for use in connection with theforegoing substrates will be suitable in the present invention. Suchmaterials include, by way of example only, nematic, chiral nematic(cholesteric), smectic and ferroelectric smectic liquid crystalmaterials. They include materials that are bistable and those that arenot bistable. They include cholesteric or chiral nematic liquid crystalshaving positive or negative dielectric anisotropy or a combination ofnegative and positive with a crossover frequency suitable for dualfrequency addressing. They include cholesteric materials having pitchlengths reflecting in the visible spectrum as well as those having pitchlengths reflecting outside the visible spectrum, including ultravioletand infrared. Preferred liquid crystal materials for use in the presentinvention are bistable cholesteric (chiral nematic) liquid crystalshaving positive dielectric anisotropy and planar and focal conictextures that are stable in an absence of an electric field. Especiallypreferred materials are nematic materials with a high birefringence anddielectric anisotropy with a chiral additive to twist the material to apitch length to reflect in the visible spectrum such as BL061, BL048 andBL131 from EM Industries of Hawthorne, N.Y.

Cholesteric liquid crystal layers are stackable as discussed in moredetail below. Light is inherently reflected by the cholesteric liquidmaterial at preselected wavelengths and bandwidth and is transparent toother wavelengths, allowing the entire area of the display to be used asa reflection surface and making maximum use of available light forbrightness. Cholesteric materials can be tuned to reflect at any desiredwavelength (λ) or color and bandwidth (Δλ) for full color displays withstacks of the primary colors red, green and blue (RGB). One can alsoemploy dispersions containing cholesteric liquid crystal-containingdroplets in a polymer matrix that reflect red, green and blue light in asingle layer.

As will be apparent to those of ordinary skill in the art in view of theinstant disclosure, the liquid crystal material will preferably bepresent in the displays of the invention in the form of liquidcrystalline layers each comprised of a liquid crystal dispersion and,most preferably, a cholesteric dispersion. There are many differentapproaches to the formation of a liquid crystal dispersion, some ofwhich have been used for cholesteric liquid crystals. To form such aliquid crystal layer, the liquid crystal can be microencapsulated orformed into emulsified droplets of liquid crystal, as discussed in moredetail below.

As noted, the liquid crystal layer will, in the preferred embodiments,be bounded by conducting electrodes. The electrodes need not beidentical. For example, in many embodiments, the electrode on thenon-viewing side of the liquid crystal will be black or some othercolor, while the electrode on the viewing side will be transparent. Inother embodiments, the electrodes on both sides of the liquid crystallayer will be transparent. In other embodiments still, an electrode orarray of electrodes can be formed integrally with the substrate or thesubstrate itself can form one of the electrodes. An advantage to beingable to use fabric substrates as discussed below, is that it enablesgreater flexibility in the manner in which the display can beconfigured.

There are potentially many methods of applying and patterning theconductors. The conductors may be printed in some specified patternusing ink jet, screen or off-set printing. Alternatively, the conductingmaterials may be sprayed or coated onto the underlying surface (such asthe dye layer, protective layer, casting layer or substrate) using amask, stencil or pretreating the surface to form a chemical mask whichallows the electrode material to only adhere to certain areas. In somecases it may be desirable to first lay down a uniform conducting coatand subsequently pattern the layer by chemically or mechanicallydeactivating regions of conductive material. In fact, it is contemplatedthat even the substrate itself can be manufactured as the conductor. Forexample, some flexible plastic materials are manufactured with an indiumtin oxide (ITO) coating that may be patterned for use as electrodes.Suitable electrode materials for application to the substrates of theinvention will be apparent to those of ordinary skill in the art in viewof the instant disclosure and include conducting polymers, carbonnanotubes, metal or carbon conductive inks, ITO and the like. Electrodematerials which are self leveling and which can be used in suitablethicknesses to obviate the need for a planarization layer areparticularly desirable. Examples of materials for use as conductingelectrodes in accordance with the present invention include Agfaconducting polymers ELP-3040, S300, and S2500 available fromAgfa-Gevaert N.V., Belgium; Carbon Nanotube materials are available fromEiKos, Inc., Franklin Mass. The aforementioned electrodes can bepatterned, formed into pixels of varying shapes or sizes, aligned intorows and columns so as to form a passive matrix and so on, all as willbe apparent to those of ordinary skill in the art in view of the instantdisclosure.

Any means for addressing the liquid crystal known in the art, andpreferably adaptable to a display having deformability may be used. Inthe preferred electrically addressable displays, the means foraddressing the liquid crystal will be drive and control electronicsoperatively linked to the electrodes for application of driving voltagesacross the liquid crystal material in accordance with any suitable drivescheme known to those of ordinary skill in the art. Examples of suitabledrive schemes and electronics include, but are not limited to, theconventional drive scheme disclosed in U.S. Pat. No. 5,644,330implemented with either bipolar or unipolar drive chips, the dynamicdrive scheme disclosed in U.S. Pat. No. 5,748,277 or U.S. Pat. No.6,154,190 for faster or lower temperature response, the cumulative drivescheme disclosed in U.S. Pat. No. 6,133,895, for near video response,and the Multiconfiguration Display Driver disclosed in the 10/782,461patent application, all of which are incorporated herein by reference.Alternatively, the means for addressing can be an optical method wherebythe image is written on the display with white light or laser light in amanner such as disclosed in H. Yoshida et al., Journal of the SID, Vol.5/3, 269-274, (1997), also incorporated herein by reference. In theseembodiments, the displays can be fabricated without patternedelectrodes. The ledges of substrates where the ends of electrodes arelocated are left accessible for interconnecting the drive electronicsand electrode layers may extend beyond the periphery of the other layersof the display for interconnecting the drive electronics, such asdisclosed in U.S. patent application entitled “Stacked Display withShared Electrode Addressing,” PCT/US05/03141, filed Jan. 28, 2005, whichis incorporated herein by reference in its entirety.

In a preferred configuration, a high resolution display device inaccordance with the invention is configured where the first conductingpolymer is printed or otherwise patterned in the form of parallel stripsto form rows of parallel conducting electrodes. The droplet dispersionis then coated on top of the rows of conductors, followed by atransparent conductor which is then printed, or otherwise coated andpatterned on top of the droplet dispersion in the form of conductivestrips (columns) in a direction perpendicular to the rows of conductorsthat are under the dispersion. In this way, a row and column matrix ofelectrodes is formed with the cholesteric dispersion in between. Voltagepulses are then multiplexed in such a way to selectively address each ofthe pixels of the display formed by the intersection of each row andcolumn. When a high-resolution image is addressed on the display filmand the voltage removed, the image will be retained indefinitely untilreaddressed to form another image.

In carrying out the invention, it will often be desirable to employ anelectrical insulation layer or layers between the electrodes in order toinsulate the conductors from each other and thereby minimize thepotential for shorting. Accordingly, for purposes of the instantinvention it is desirable to select materials that can be coated,printed, sprayed or otherwise laid down in a layer before and/or afterthe electro-optically responsive liquid crystal layer. The insulationlayer must not significantly detract from the deformability or optics ofthe display. In accordance with preferred embodiments of the invention,materials such as gelatin or latex are employed. Some particularlypreferred insulating materials are polyurethane latex materials such asWITCOBOND W232 (available from Crompton Corporation, CT). Although aninsulation layer such as gelatin is optional, experiments show that itleads to a decrease in the switching voltage on the order of 10-15 volts(frequency=250 Hz) when the liquid crystal layer is a cholestericdroplet dispersion. Without being bound by theory, this may be becausethe gelatin layer is enhancing the dielectric properties of the emulsionthrough the increase of the dielectric constant.

The use of one or more durable protective coatings (e.g., top coats)obviates the need to use a substrate, thereby enhancing both theflexibility and durability of the display film. Desirable protectivecoatings will be materials that will provide a tough, scratch andwear-resistant coating over at least a portion, and preferably all, ofthe uppermost surface of the display, but do not materially interferewith the optics of the system. Likewise, the most desirable protectivecoating materials will maintain the deformability of the system. Thoseof ordinary skill in the art will be able to select suitable protectivecoating materials in view of the instant disclosure; preferred materialsinclude acrylic or silicone paints, UV curable adhesives, PVA, latexmaterials and the like. Because some protective coatings will includesolvents or other components which may be harmful to the electrodes orother elements of the display, in carrying out the invention it may bedesirable to select an isolation layer material that will protect theother display elements from harmful components of the adjacent coat. Thelaminated display film of the present invention includes within itsscope various additional layers in different sequences, numbers andlocations throughout the display.

As will be apparent to those of ordinary skill in the art, displaysaccording to the invention can be formed in many differentconfigurations using some or all of the foregoing component layers. Forexample, the display materials may only appear on one side of a fabricsubstrate leaving the other side untouched, or portions of the displaymay be partially imbibed into and integrally formed with the substrate.The minimum requirements for the electrically addressable transferdisplay films of the invention are at least one liquid crystal layer andat least one adjacent conducting electrode layer; the liquid crystallayer is sandwiched between the film electrode layer and anotherconducting electrode layer that is a component of the display film or aconductive electrode layer that is applied to, on or imbibed into thesubstrate. Beyond this, there are multiple possible configurations andcombinations which can effectively take advantage of the flexibilityand/or drapability of the substrates according to the invention as willbe apparent to those of ordinary skill in the art in view of the presentdisclosure.

The fabrication of the inventive display film involves printing, coatingor other deposition means to form the liquid crystal material, displayelectrodes as well as any insulating, isolation or other coatings. Theselayers in a preferred embodiment are built on a casting layer that isremoved from the release surface once the multi-layered laminate hasbeen dried or cured. In view of the instant disclosure those of ordinaryskill in the art will be able to select and employ suitable coating,printing and deposition techniques including, but not limited to, airbrushing, ink jet, spin coating and spray printing, optionally inconjunction with various masks or stencils known in the art, screenprinting, photolithography, chemical masking and so on, depending uponthe particular layers, substrates or display elements used. It iscontemplated that any contact or non-contact method of applying coatingsand conductors known in the art will be suitable for use in accordancewith the instant disclosure.

2. Liquid Crystal Dispersions

An encapsulation process involves emulsification of a cholesteric liquidcrystal in water with a waterborne polymer. Encapsulation of cholestericliquid crystals by emulsification was practiced even before theinvention of bistable cholesteric displays. As early as 1970,cholesteric materials were emulsified for making cholesteric thermal andelectrical responsive coatings as discussed in U.S. Pat. No. 3,600,060,incorporated herein by reference. More recently, emulsification methodshave been refined by Stevenson et al., at Kodak to make cholestericdroplets that are very uniform in size, as disclosed in U.S. Pat. No.6,423,368 B1, incorporated herein by reference. The most commonemulsification procedure basically involves a liquid crystal beingdispersed in an aqueous bath containing a water-soluble binder materialsuch as de-ionized gelatin, polyvinyl alcohol (PVA) or latex. Water actsas a solvent and dissolves the polymer to form a viscous solution. Thisaqueous solution does not dissolve the liquid crystal, and they phaseseparate. When a propeller blade at a sufficiently high speed stirs thissystem, micron size liquid crystal droplets are formed. Smaller liquidcrystal droplets form at higher stirring speeds as disclosed in P.Drzaic, Liquid Crystal Dispersions, World Scientific Publishing Co.,Singapore (1995), incorporated by reference. The molecular weight of thewater-soluble polymer is also a factor affecting the droplet size. Afterthe droplets are formed, the emulsion is coated on an underlying layeror substrate and the water is allowed to evaporate. There are manydifferent emulsification procedures. In preferred embodiments, one ormore of PVA, gelatin and latex, preferably urethane based latex, areused to form the binder. The emulsification method has the advantagethat the droplet dispersions may contain a very high percentage ofcholesteric material. Those of ordinary skill in the art will be able toselect suitable materials and methods for providing emulsified liquidcrystal droplet layers for use in accordance with the present inventionin view of the instant disclosure.

Microencapsulation is a yet another process for preparing dropletdispersions as seen, for example, in U.S. Pat. No. 6,271,898,incorporated herein by reference. While this procedure can be morecomplex and material sensitive, it can nonetheless provide more controlover droplet size and molecular anchoring conditions for the cholestericliquid crystal. In this case the liquid crystal droplet is coated by ashell isolating it from the binder. It may be possible to process thedroplet particles in the form of a dry powder which is later dispersedin a suitable binder for coating. Other types of dispersions may be aregular array of polymer pockets filled with liquid crystalline materialand sealed on the top by a phase separation process as disclosed in, forexample, D. J. Broer et al, Society for Information Display 2004Proceedings, pp 767.

3. Multiple Liquid Crystal Layers

The inventive display film can be fabricated by coating two or morecholesteric liquid crystal dispersion layers over one another. One ormore conducting electrode layers are located between adjacent liquidcrystal layers. A full color display can be made by stacking threeliquid crystal layers having pitch lengths that reflect red, green andblue light, respectively. With only one electrode layer between eachliquid crystal layer, the display is electronically addressed by ashared electrode addressing scheme possible with bistable cholestericdispersions as disclosed in the U.S. patent application entitled“Stacked Display with Shared Electrode Addressing,” PCT/US05/03141. Aninfrared reflective display is possible where at least one of thedroplet dispersion layers reflects in the infrared, such as might beused for night vision purposes. For color, enhanced brightness orinfrared applications such as those described in U.S. Pat. No.6,654,080, incorporated herein by reference, stacks of coatings arrangedas disclosed therein can be employed in accordance with the instantinvention. A multiple color display can also be prepared with a singledispersion layer wherein each pixel is divided into different primarycolors such as red, green and blue, for additive color mixing. Thepatterned colors can be achieved as described, for example, in U.S. Pat.No. 5,668,614, incorporated herein by reference.

In order to increase brightness of a cholesteric liquid crystal layer ofthe display, both the left and right circular components of the incidentlight should be reflected. There are two methods to accomplish this: tolayer a cholesteric material of one handedness on top of the other or toinsert a half wave plate in between two layers of the same handedness.One aspect of the invention coats subayers of cholesteric materials ofdifferent handedness (left hand—LH and right hand—RH) on top of oneanother in the formation of the liquid crystal layer reflecting acertain wavelength of electromagnetic radiation. The coatings areimmiscible so that the droplet structures of the two different materialsare not destroyed in the coating or drying process. The encapsulantsurrounding the droplets is impermeable to the cholesteric material tolimit molecular diffusion in that cholesteric material of one handednessdissolving into the other will destroy its desired optical properties.An optional barrier layer is disposed between LC sublayers. In the caseof the full color display, each of the red, green and blue reflectingliquid crystal layers may be composed of LH/RH sublayers to increasebrightness.

4. Compositions and Layer Thicknesses

The layers of the multilayer film can have various compositions as wouldbe apparent to those skilled in the art in view of this disclosure. Byway of example only, and without limiting the present invention,suitable compositions of the various layers of the multilayer filminclude solvent-based, water-based and water-borne polymers for theplanarization layer; solvent-based, water-based and water-borne polymersand thin plastic sheets, including PET, PC, PEN for the casting layer;water-borne polymers, including polyurethane and acrylic latexes,water-soluble polymers, including gelatin, polyvinyl alcohol, andpolyvinyl acetate for binder material which surrounds the liquid crystaldroplets; cross-linking agents, including materials based on aziridine,lactic acid chelates, formaldehyde, glutaradehyde as additives to bindermaterial to control binder properties and various surfactants, includingsurfactants based on silicone polyether copolymers, alkylarylpolyethers, alcohol ethoxylates (Triton X-100, Triton CF-10, DC 5098,alkanol) as additives to binder material to control binder properties.

The layers of the multilayer film can have various magnitudes ofthickness and relative thicknesses to one another. Those skilled in theart will appreciate in view of this disclosure various layer thicknessesthat may be suitable for use in the present invention. By way of exampleonly, and without limiting the present invention, suitable thicknessesof the casting layer are less than 20 microns and, in particular, in arange of 5 to 15 microns. Suitable thicknesses of the adhesive layer arein a range of 10 microns to 75 microns and, in particular, less than 25microns. Suitable thicknesses of the electrode layer are governed, forexample, by the transparency and resistivity of the conducting polymer.Normally the desired resistivity is less that 1000 Ohms per square andtransparencies above 90% are desired. This typically results in athickness less than 1.0 micron for the electrode layer.

B. Transfer Display Film

1. General

Liquid crystal displays sold in the marketplace today are fabricated bybuilding the display on a substrate that forms a part of the display.Conventional displays include two substrates that sandwich the liquidcrystal material in between. Lines of electrodes may be patterned ontothe substrates. The substrates may include treatment such as rubbing ofchemicals applied to the substrates to affect the alignment of theliquid crystals. In contrast, the inventive lift off (e.g., transfer)display film includes some or all of the components of a typical liquidcrystal display, but is built up on a release liner during fabricationand a substrate need not be incorporated as an element of the displayfilm. The display film is then lifted off the release liner andtransferred onto a substrate. The transfer display film can be made withsome of the components that make up a complete display, for example,with one or two electrode layers on either side of the liquid crystal.For example, a transfer display film containing a single electrode layercan be transferred to a substrate having the other electrode layer on itand the drive electronics can be added when the transfer film islaminated onto the substrate. On the other hand, the transfer displayfilm may include all elements of an operable display except for someelements of the drive electronics, and then transferred onto a substratecontaining drive electronics. Those skilled in the art will appreciatethat these and other variations in the number and types of componentsand when they are added during the steps of the fabrication process,fall within the scope of the present invention.

The transfer display film may include a layer that facilitates bindingof the transfer film to the substrate. This can include an adhesionlayer as a part of the transfer display film. Instead of or in additionto the adhesion layer, the transfer display film may include apreparation layer that enables binding to an adhesion layer. Thepreparation layer may match indices of refraction of adjacent layers. Ifthe adhesion layer is formed on the substrate to which the transferdisplay film will be transferred, the transfer display film may includea preparation layer that accommodates the solvent of the substrateadhesion layer.

A transfer display film as described above has the following advantages.It can be laminated on a rough surface such as cloth, paper or otheruncommon substrates for commercially available liquid crystal displays.The lamination process will not alter the uniform spacing between theelectrodes. The substrate on which the film will be laminated can bemanufactured independently of the display film, making available a widevariety of materials or shapes not available for substrate use before.The manufacturing facility of the display film can be simplified and oflower cost since it does not have to be specific to the substrate. Thetransfer display film can be laminated on substrates that otherwisecould not contain a display in that they cannot be processed in a cleanroom environment. The display film can be transferred onto a backplanethat contains a portion of the display elements and/or drive electronicssuch as, for example, an active matrix backplane or the orthogonal rowor column conductive lines of a passively driven display.

An advantage of the invention is that the manufacturing process isindependent of the substrate, unlike any display manufacturing processbeing currently used. Another advantage is that the display film may betransferred onto any of a wide variety of substrates, such as cloth,which was not possible before. The substrate may possess a roughsurface. However, the film can be laminated so that the electrodespacing is maintained and the display is functional so long as thesurface does not rupture the display film. The display film can be madepliable and rugged. The inventive display film can be stretched orrolled up, is suitable for lamination on plastic, woven fabric material,etc. or may even be specifically designed for lamination on an activematrix substrate.

Cholesteric materials are particularly well suited for a display film inthat they can be made as droplet dispersions that can be coated orprinted and are self-sealing to contain the cholesteric liquid crystalin the film. Cholesteric liquid crystal materials may be bistable,possessing planar and focal conic textures that are stable withoutapplication of an electric field. Once an image is formed, no electricfield is required to maintain the image. That is to say, a voltage belowthreshold voltage can be applied to the liquid crystal layer withoutchanging its planar or focal conic textures. The image will remainindefinitely until it is updated by additional voltage pulses applied tothe pixels above the threshold voltage. Cholesteric materials are fielddriven, as opposed to current driven, requiring near negligible currentto change their optical state. As such, the conducting electrodes can becomposed of such materials as conducting polymer or carbon nanotubesthat can be printed or coated into a film, which generally possess lowtransparency/conductivity ratios. Other droplet dispersion systems suchas nematics and ferroelectrics also offer the possibility for use as atransfer film.

2. Drapable Liquid Crystal Transfer Display Film

One aspect of the display film of the present invention is that thelift-off film itself is flexible and can be drapable. Also, the lift-offfilm can be transferred onto a drapable substrate. This inventioninvolves a substantial advance in addressable liquid crystal displayswherein, by forming the displays as a drapable film or combining thetransfer display film with a drapable substrate, the display itself isdrapable. Such substrates include textiles or fabrics made of natural orman-made fibers such as cloth or paper, as well as non-fibrous materialssuch as flexible or even drapable thin polymeric sheets or films.Advantageously, the substrate need not be transparent. With deformablesubstrates, cholesteric or other liquid crystal displays are madeflexible, rugged and can even be sewn into or onto clothing to provide awearable display. In fact, the display itself can form the material usedto make the clothing or other fabric construct. A display with thedrapability of cloth provides a new dimension to display technologyenabling display applications that were not previously possible. Suchdisplays can conform to three dimensional structures or flex and foldwith a garment or other fabric construct containing the display. To thisend, the displays according to the invention are operatively deformable,meaning that they will function even though they are or have beendeformed. In preferred applications, the displays according to theinvention will be operatively drapable such that they can have folds andpossess a measurable drape coefficient.

The formability of the display film and of fabric or other drapablesubstrate material onto which the display film is transferred, can bedefined as its ability to re-form from a two-dimensional shape to asimple or complex three-dimensional shape. The drape coefficient is usedto describe the degree of 3-D deformation when the fabric specimen isdraped over a drapemeter as described, for example, in the publication:“Effect of Woven Fabric Anisotropy on Drape Behavior,”ISSN 1392-1320,Materials Science (Medziagotyra), Vol. 9, No. 1, pp. 111-115 (2003) byV. Sidabraitre and V. Masteikaite, or “Modeling the Fused Panel for aNumerical Simulation of Drape” Fibers and Textiles, Vol. 12, pages 47-52(2004), by S. Jevsnik and J. Gersak, incorporated herein by reference.Drapability is a phenomenon that occurs when a material such as acurtain, flag, table cloth or flared skirt hangs from an object. Thedrape coefficient, DC, describes any deformation between draped andundraped material. In terms of percentage, it is described by the ratio:DC=100(S_(P)−R₁ ²)/(R₂ ²−R₁ ²) were R₂ is the radius of a circular cutof non-deformed fabric; R₁, the radius of a horizontal disc holding thefabric, and S_(P) the projected area of the draped specimen, includingthe part covered by the horizontal disc. The value of DC varies betweenzero and 100%. Since the value of DC can depend on the values selectedfor R₁ and R₂ of the drapemeter, we follow others in taking R₁=9 cm andR₂=15 cm. The larger the value of the drape coefficient, the stiffer thefabric and more difficult to reform. Alternatively, the lower the valueof DC, the easier to reform and adapt to shapes. Some examples ofdesirable fabric substrate materials include silk, cotton, nylon, rayon,polyester, Kevlar, or similar materials made of fibrous material formedby woven and non-woven means having the deformability of cloth. Someexamples of fabrics having the desired drapability are shown in Table I,which shows measured values of the drape coefficient, DC, for variousfabric materials made with R₂=15 cm and R₁=9 cm. The data on thematerials identified with an asterisk (*) were obtained from thepublication “The Dependence of Fabric Drape on Bending and ShearStiffness, J. Textile Institute, Vol. 56, pp. 596-606 (1965) by G. E.Cusick, incorporated herein by reference. The other materials wereobtained from Jo-Ann Fabrics, Cuyahoga Falls, Ohio and Hudson, Ohio, andthe DC values measured.

TABLE I Weight Thickness Fabric (g/m²) (mm) DC(%) *Woven dress fabric,spun viscose 231 0.36 67.8 rayon *Woven dress fabrics, spun viscose 1420.41 36.9 rayon *Plain woven 1.5 den spun viscose 196 0.45 32.6 rayon*Plain woven continuous-filament 226 0.46 24.7 acetate and rayon *Wovendress fabric cotton 115 0.20 75.5 *Woven dress fabric cotton 105 0.3197.2 *Plain woven, continuous-filament 96 0.20 49.9 polyester fiberPolyester from Jo-Ann Fabrics 186 0.3 14 Polyester-65%, nylon 35% from116 0.17 49 Jo-Ann Fabrics Polyester, satin from Jo-Ann 128 0.21 52Fabrics

As will be apparent to those of ordinary skill in the art in view of thepresent disclosure, any deformable material having the desiredflexibility or drapability and capable of supporting the displayelements as disclosed herein will be suitable for use in the invention.In some preferred embodiments, the fabric substrate may be a compositeor, more preferably, a fiber reinforced composite such as cotton andpolyisoprene. An example of such composites is a raincoat where thecotton provides the feel and drapability of cloth and polyisopreneprovides water resistance. Another example is rayon and neoprene used asa light shield against laser light such as that obtained by Thorlabs,Inc. (NJ) catalog # BK5. Composites can be useful substrate materialsfor many of the preferred displays of the invention.

In many preferred embodiments, the substrate material isnon-transparent. While black is a preferred color, other colors such asdark blue, green or some other color may be used to additively mix withthe reflective color of the cholesteric liquid crystal to provide thedesired color of text or other image addressed on the display. Thesubstrate material itself may be substantially clear or transparent butthe substrate made non-transparent by adding a black coating or dye torender it opaque, translucent or non-transparent as required for thebackground of the display. The image on a reflective cholesteric displayis viewed against the background. It is therefore important that thebackground absorb unwanted light and not provide light that competeswith or washes out light reflected from the cholesteric liquid crystal.Most fabrics are non-transparent. There are many examples of deformablesheet materials that are not made of fibers such as polymer films. Ifthe sheet is thin enough, these films may also be drapable. An exampleof a polymer film that is non-transparent and very drapable is blackstatic cling polyvinyl chloride sheet material from Graphix Plastics,Cleveland Ohio. Other examples of non-fibrous and drapable plasticsheets having the desired drapability are shown in Table II, which showsmeasured values of the drape coefficient, DC, for various non-fibroussheet materials (R₁=9 cm and R₂=15 cm). The value of the drapecoefficient was measured by photographing from above, the drape of thespecimen of radius R₂ draped over a pedestal of radius R₁ under aweighed disk of the same radius. The areas of the projected image of thedrape in the circle of radius R₂ were obtained from the digitalphotograph. In all cases, the drape showed the characteristic folds.

TABLE II Weight Thickness Sheet Material (g/m2) (mm) DC(%) Blackpolyvinyl chloride from 189 0.15 52 Graphix Plastics Clear DuraLar(general purpose 18.1 0.013 68 polyester) Clear DuraLar (generalpurposed 32.9 0.025 95 polyester) Clear DuraLar (general purpose 73.70.050 98 polyester)

Sheet materials which are too thick do not exhibit drape but may bend orbe flexed about one axis such as, for example, being rolled up. Anexample is 5 mil (0.125 mm thick) Clear DuraLar (polyester) or 5 milthick Teijin Limited polycarbonate ITO coated foil (SS120-B30). Such 2-Ddeformation materials can be rolled up but do not reflect the nature ofdrape. It should be noted, however, that these and similar films will besuitable for certain embodiments of the invention where drapability isnot required. For example, where only a flexible display is desired,such films can be rendered black or otherwise non-transparent for use asa substrate by coating it with a black Krylon paint.

It will be apparent from the following that while advantages of theinvention are realized by the presentation of a deformable liquidcrystal display, a principal contributor to the realization of thisadvantage is the provision of an electrically addressable liquid crystaldisplay on a single substrate. Electrically addressable displays on themarket today employ at least two substrates which, as noted above, aregenerally rigid, with the liquid crystal sandwiched between them. Thesedisplays are, in general, manufactured by batch processing methods.

In accordance with preferred embodiments of the present invention, adisplay film is fabricated by a sequence of layers on a release liner bycoating, printing or lamination techniques suitable for the webprocessing methods necessary for low cost, high volume production.Fundamentally, these layers consist of a first conductive layer followedby a layer of an electrically responsive droplet dispersion such as apolymer dispersed cholesteric liquid crystal, followed next by atransparent conductive layer. Insulation coatings are often neededbetween the cholesteric dispersion and electrodes to avoid electricalshorts between the electrodes. A durable protective layer is coated tofinalize construction of the display film. In some cases an isolationlayer is required between some of the coatings to avoid damage bysubsequent coatings, such as may be caused by a chemical reactionbetween coating solvents or other components. Likewise, preparationcoatings between various layers may be necessary to promote wetting andadhesion of the subsequent coat. In some embodiments, the coatings oftenserve multiple functions, such as where the first conductive coat mayalso serve as a preparation coat to smooth the surface.

As noted, the liquid crystal layer will, in the preferred embodiments,be bounded by conducting electrodes. The electrodes need not beidentical. For example, in many embodiments, the electrode on thenon-viewing side of the liquid crystal will be black or some othercolor, while the electrode on the view side will be transparent. Inother embodiments, the electrodes on both sides of the liquid crystallayer will be transparent. In other embodiments still, an electrode orarray of electrodes can be formed integrally with the substrate or thesubstrate itself can form one of the electrodes. The multilayer film isthen lifted off the release liner and transferred to a flexiblesubstrate.

Transferring the film onto rough textiles, other rough fabrics or otherrough substrates or layers could employ a planarization coating to atleast partially smooth the surface. This may be followed by apreparation coating or sequence of such coatings to further smooth thesurface of the fabric as well as adjust its color, resistivity, wettingand adhesive properties with respect to the first conductive layer.However, it is believed that the inventive display film can be appliedto all but the roughest surfaces without the need for planarization ofthe surface. The inventive transfer film exhibits good durability andtoughness during the fabrication process and maintains the gap thicknessof the liquid crystal layer between adjacent electrode layers.Typically, only those surfaces that are so rough that they couldpuncture the liquid crystal layer, would include a planarization layeron the rough surface.

Planarization of rough surfaces can be conducted in various ways asdisclosed in the U.S. Application Ser. No. 60/565,586 and Ser. No.11/006,100. A preferred manner of planarizing a surface in accordancewith the invention is the addition of a planarization layer. Aplanarization layer is a coating of material which, when applied to therough substrate or other rough layer such as to a rough casting layer,will tend to smooth out the most dramatic fluctuations in the roughsurface so as to provide a generally smooth, though not necessarilyflat, surface onto which to deposit the next layer. Preferred materialsfor use as a planarization layer in accordance with the invention aregelatin, neoprene and latex materials such NeoRez R967 available fromNeoResins, MA. The planarization layer also may be a polymeric sheetsuch as PET.

As will be apparent to those of ordinary skill in the art, display filmsaccording to the invention can be formed in many differentconfigurations using some or all of the foregoing component layers. Forexample, the display film may only appear on one side of the fabricleaving the other side untouched, or the display film may be partiallyimbibed into and integrally formed with the flexible substrate, as bytransferring the display film onto a heated fabric substrate.

3. Other Substrates

A self-powered display may be achieved by using a solar panel as thesubstrate or a component of the substrate whereby light that is notreflected by the cholesteric material can be absorbed in the solar panelfor conversion into electrical power for powering the display.

It is also conceived that an active matrix substrate could be employedto create an actively driven cholesteric display, whereby the variousdisplay elements of the transfer film are laminated onto the activebackplane.

Further still, an optically addressed display is achieved by placing aphotoconductive sheet over the lower conducting electrode. With acontinuous voltage applied to the electrodes, light impinging thedisplay film will locally alter the resistivity of the photoconductorand drive the display film. Such a display construction avoids the needof patterning the electrodes. The display can include an upper and lowerunpatterned electrode. The display can be addressed by an image suitablyfocused on the film, or written with a scanned laser beam as describedin the publication “Reflective Display with Photoconductive Layer andBistable Reflective Cholesteric Mixture” Journal of the SID, Vol. 5/3,pages 269-274 (1997) by J. Yoshida et al., incorporated herein byreference. Of course, other veneered stacks are possible depending ondesired display.

VI. SUMMARY OF THE INVENTION

In general, one embodiment of the present invention features a liquidcrystal transfer display film comprised of a plurality of layers thatare prepared on, cured and lifted from a release surface and thentransferred to a substrate. The plurality of stacked layers comprise atleast one liquid crystal layer and at least one electrically conductivelayer near the liquid crystal layer. More specifically, the stackedlayers of the display film are stacked in a sequence comprising acasting layer, a first electrically conductive layer, the liquid crystallayer and a second electrically conductive layer. In another aspect ofthe invention, the display film comprises a casting layer applied on ornear the release surface on which the other layers of the display areprepared, the casting layer being selected from the group consisting ofa preparation layer, the at least one electrically conductive layer, anadhesive layer, a planarization layer, the at least one liquid crystallayer, an isolation layer and combinations thereof.

The liquid crystal layer comprises a dispersion of liquid crystal in apolymer matrix. The liquid crystal layer may comprise liquid crystalthat is bistable and/or can be contained in droplets. For example,suitable liquid crystal material is cholesteric liquid crystal materialthat is bistable in the display film, i.e., it exhibits planar and focalconic textures that are stable in an absence of an electric field. Apreferred dispersion includes such cholesteric liquid crystal materialdispersed in the polymer matrix. The dispersion is selected from atleast one of an emulsion and microencapsulated liquid crystal material.

The liquid crystal display film may include one, two, three or moreliquid crystal layers. The layers reflect visible and/or infraredelectromagnetic radiation. The display can include liquid crystal thatreflects red, green and blue light to form a full color liquid crystaldisplay. The full color display can comprise stacked red, green and bluereflecting liquid crystal layers. The display film may also includethree coplanar regions that include droplets containing red, green andblue reflecting liquid crystal material. The display film may exhibitimproved brightness through the use of cholesteric liquid crystalmaterial having right and left handed twist sense. This liquid crystalmaterial having both right and left handed twist sense may be located ina single layer or in two layers that may be separated by a barrier layerthat prevents diffusion between the layers. If the display film includestwo or more liquid crystal layers, a barrier layer may be used toprevent diffusion of liquid crystal material between the layers. Thisbarrier layer could also function as an electrically insulating layer.

Referring to specific aspects of the layers of the inventive displayfilm, an optical layer is located between the casting layer and theliquid crystal layer that matches indices of refraction of adjacentlayers. A light absorbing layer is used when the portion of the displaydownstream of the lowermost liquid crystal layer (e.g., the substrate)is not sufficiently light absorbing. At least one of the electricallyconductive layers can comprise an electrical conductor formed of aconductive polymer or carbon nanotube material. An electrical insulationlayer is disposed between a liquid crystal layer and an adjacentelectrically conductive layer. A protective layer may be employed overthe second electrically conductive layer, which strengthens the displayfilm. The protective layer can be optically clear or opaque. The displayfilm may be mounted to the substrate near the side of the film where theprotective layer is located or on the other side of the display film.The display film may include an adhesive layer. A preparation layer maybe disposed between the adhesive layer and the other layers of thedisplay film. The electrically conductive layers can be patterned orunpatterned. One electrically conductive layer contains parallel linesof row or column conductors and another electrically conductive layercontains parallel lines of the other of row and column conductors. Aliquid crystal layer is sandwiched between the electrically conductivelayers. The lines of row conductors are arranged orthogonal to the linesof column conductors. The display film may include one electricallyconductive layer and the substrate may include another electricallyconductive layer, whereby the liquid crystal layer is sandwiched betweenthe film electrically conductive layer and the substrate electricallyconductive layer. Of course, the liquid crystal layer may also besandwiched between adjacent electrically conductive layers of thedisplay film. The liquid crystal layer can be electrically addressed bydrive electronics connected to the electrically conductive layerseffective to produce images from the display. The substrate may comprisean active matrix device that can address a liquid crystal layer of thedisplay film. In this case an unpatterned electrically conductive layeris disposed on the side of the liquid crystal layer remote from theactive matrix device. The active matrix device can electrically addressindependent pixels of the liquid crystal layer(s) as with a plurality ofthin film transistor elements.

The substrate can have numerous variations. The substrate includes asolar panel effective to form a self-powering display. In this case nolight absorbing layer would be disposed upstream of the solar cell in adirection of incident light. The solar cell could form a back of thedisplay device and absorb light that passes through the liquid crystallayer or layers of the display. The substrate may comprise aphotovoltaic and conductive layer adapted to enable the liquid crystallayer to be optically addressed when an electric field is applied to theliquid crystal layer between the conductive layers of the film andphotovoltaic.

The invention is directed to the lift off display film itself, prior tobeing transferred to a substrate, to the transfer display film that istransferred to a substrate and to a device that includes the transferdisplay film. In addition, the invention pertains to a device thatcomprises drive electronics for electrically addressing the liquidcrystal layer between adjacent electrically conductive layers.

Many additional features, advantages and a fuller understanding of theinvention will be had from the accompanying drawings and the detaileddescription that follows. It should be understood that the above Summaryof the Invention describes the invention in broad terms while thefollowing Detailed Description describes the invention more narrowly andpresents preferred embodiments that should not be construed as necessarylimitations of the broad invention as defined in the claims.

VII. BRIEF DESCRIPTION OF THE DRAWINGS

FIGS. 1 and 2 a are side cross-sectional views of the fabrication of oneaspect of a display film constructed in accordance with the inventionand FIG. 2 b is a side cross-sectional view of the display film of FIG.2 a transferred onto a substrate;

FIGS. 3 and 4 a are side cross-sectional views of the fabrication ofanother aspect of a display film constructed in accordance with theinvention and FIG. 4 b is a side cross-sectional view of the displayfilm of FIG. 4 a transferred onto a substrate, while FIG. 4 c is a sidecross-sectional view of a variation of the display shown in FIG. 4 b;

FIGS. 5 and 6 a are side cross-sectional views of the fabrication ofanother aspect of a display film constructed in accordance with theinvention and FIG. 6 b is a side cross-sectional view of the displayfilm of FIG. 6 a transferred onto a substrate;

FIGS. 7 and 8 are side cross-sectional views of the fabrication ofanother aspect of a display film constructed in accordance with theinvention and FIGS. 9 a-9 c are side cross-sectional views of thedisplay film of FIG. 8 transferred onto various substrates, while FIG. 9d is a side cross-sectional view showing a variation of the display ofFIG. 8;

FIGS. 10 and 11 a are side cross-sectional views of the fabrication ofanother aspect of a display film constructed in accordance with theinvention and FIG. 11 b is a side cross-sectional view of the displayfilm of FIG. 11 a transferred onto a substrate, while FIG. 10 a is aside cross-sectional view of a variation of the display of FIG. 10;

FIGS. 12 and 13 a are side cross-sectional views of the fabrication ofanother aspect of a display film constructed in accordance with theinvention and FIG. 13 b is a side cross-sectional view of the displayfilm of FIG. 13 a transferred onto a substrate;

FIGS. 14 and 15 a are side cross-sectional views of the fabrication ofanother aspect of a display film constructed in accordance with theinvention and FIG. 15 b is a side cross-sectional view of the displayfilm of FIG. 15 a transferred onto a substrate;

FIGS. 16 and 17 a are side cross-sectional views of the fabrication ofanother aspect of a display film constructed in accordance with theinvention and FIG. 17 b is a side cross-sectional view of the displayfilm of FIG. 17 a transferred onto a substrate, while FIG. 16 a is aside cross-sectional view of a variation of the display of FIG. 16;

FIGS. 18 and 19 a are side cross-sectional views of the fabrication ofanother aspect of a display film constructed in accordance with theinvention and FIG. 19 b is a side cross-sectional view of the displayfilm of FIG. 19 a transferred onto a substrate;

FIGS. 20 and 21 a are side cross-sectional views of the fabrication ofanother aspect of a display film constructed in accordance with theinvention and FIG. 21 b is a side cross-sectional view of the displayfilm of FIG. 21 a transferred onto a substrate;

FIGS. 22 and 23 a are side cross-sectional views of the fabrication ofanother aspect of a display film constructed in accordance with theinvention and FIG. 23 b is a side cross-sectional view of the displayfilm of FIG. 23 a transferred onto a substrate;

FIGS. 24 and 25 a are side cross-sectional views of the fabrication ofanother aspect of a display film constructed in accordance with theinvention and FIG. 25 b is a side cross-sectional view of the displayfilm of FIG. 25 a transferred onto a substrate; and

FIG. 26 is a perspective exploded view illustrating the fabrication ofthe conductive electrode layers of the inventive display and mounting toa substrate.

VIII. DETAILED DESCRIPTION

One embodiment of the invention is a monochrome bistable cholestericreflective lift off or transfer display film that can be transferred tofabric, polymer, or other substrate that is transparent or opaque. FIG.1 shows a display film 10 containing various layers that make up thefilm. The film is fabricated by coating or casting each of the layers ona surface that can serve as a release liner 12 in the followingsequence. An optional casting layer 14 is first coated or laminated ontothe release liner 12. The casting layer serves several purposes. Thecasting layer is a film that, once dried or cured can be removed fromthe release liner. The casting layer also provides a suitable surfacefor wetting the next coating in the sequence which can be an optionalopaque light absorbing layer 16 to serve as a dark background.Alternatively, if a dark background is not used, the next layer may beone of the display electrode layers. The casting layer is sufficientlyrugged to be lifted off the release liner and subsequently laminatedonto a substrate.

The light absorbing layer 16, usually black in color, is coated onto thecasting layer. The light absorbing layer adheres to the casting layerand, in this embodiment, serves to absorb unwanted light passing throughcholesteric liquid crystal layer 18. The resulting display is observedfrom above in the direction of the arrow (FIG. 2 b). The material of thelight absorbing layer serves to wet the next coating in the sequence,the lower conductive electrode layer 20.

The lower conductive electrode layer 20 is coated or printed andsuitably patterned on the light absorbing layer. In this embodiment, theconducting material does not have to be transparent but is desired notto be reflective. Carbon based materials and conducting polymers aresuitable as long at they provide sufficient conductivity, for example,less than 1000 Ohms/square resistivity, a parameter also controlled bythe thickness of the layer. Carbon based materials and conductingpolymers might be suitable in that, often they can be printed to form adesired electrode pattern.

An optional electrical insulation layer 22 over the conductingelectrodes is advantageous in preventing electrical shorting. However,if the cholesteric liquid crystal is dispersed in a binder or polymermatrix that is itself sufficiently electrically insulating, theinsulation layer may be omitted. The insulation layer is preferably lessthan 1.0 micron thick in order to maintain suitable drive voltages.

The cholesteric liquid crystal layer 18, which is in the form of adispersion composed of liquid crystal dispersed in a polymer matrix, isthen coated over the insulation layer. The liquid crystal dispersion canbe made from any of several different processes such as emulsificationor microencapsulation processes. A preferred dispersion is prepared froma latex emulsion since these binders possess desired wetting andadhesion properties for coating. For the cholesteric liquid crystal, thedroplet size should be large enough, for example, greater than 1.0micron, to allow bistability. The term, droplet, used herein can haveany of a variety of shapes including spherical, elliptical, andamorphous shapes. The thickness of this liquid crystal coatingdetermines the drive voltage of the display as well as the displaybrightness. To optimize brightness, it is desired that this layer be atleast 4.0 microns in thickness; however, to maintain moderate to lowdrive voltages, the layer should be less that 15 microns thick dependingon the physical properties of the liquid crystal material.

A second optional electrical insulation layer 24 is advantageous inpreventing electrical shorts. This layer may also serve as an isolationor wetting layer for the transparent conducting layer 26.

The transparent conducting layer 26 is printed or coated and suitablypatterned to serve as the upper electrode. Transparent conductingpolymers or carbon nanotube materials are suitable for this purpose. Thetransparency-to-conductivity ratio depends on the thickness of thecoating. If response speed of the display is not an issue, a resistivityas high as a few thousand Ohms/square is suitable.

An optional clear protective layer 28 is applied to the transparentconductive layer 26. The clear protective layer or “clear coat” 28 isadvantageous in ruggedizing the display and protecting it from theenvironment. The term “clear coat” finds analogy to clear coats used asouter protective coatings on the paint finish of automobiles.

The display film is cured. Then, as shown in FIG. 2 a the cured displayfilm is lifted from the release liner 12. As shown in FIG. 2 b, thedisplay film is then transferred or laminated onto a substrate 30.

Another aspect of the invention is similar to the foregoing display filmbut employs an adhesive layer 32 and/or preparation layer 34. Thisdisplay film is shown in FIG. 3 where like reference numerals describesimilar components throughout the several views. Display componentshereafter that are the same or similar to those previously described,will not be described in detail again, it being understood that theprevious detailed description of materials, characteristics and featuresof the display components applies equally to subsequent displaycomponents. The only difference between the display film shown in FIG. 3and the display film shown in FIG. 1, is the addition of an adhesionlayer and an optional preparation layer sometimes needed to present asmooth surface between the adhesion layer and the next layer in thedisplay which may be a casting layer, if needed, or the conductiveelectrode. The preparation layer may also serve as an isolation layer toisolate the other display elements from solvents in the adhesion layer.

As shown in FIG. 4 a, once the display film has cured it is lifted fromthe release liner. The adhesive layer 32, albeit having the ability topossess relatively strong adhesive properties, nonetheless does not bindto the release liner 12 with high adhesion. The release liner may have awaxy or other surface that the adhesive of the adhesion layer does notbind strongly or the adhesive and release liner materials may havecompositions that prevent wetting of the adhesive material to therelease liner. As shown in FIG. 4 b, the display film is thentransferred or laminated onto a substrate 30. The adhesive layer 32binds the display film to the substrate 30 with a desired level ofadhesion.

In a specific design, the adhesive layer 32 is composed of pressuresensitive adhesive and has a thickness, for example, of about 25microns. The layer 34 is a preparation or casting layer. One suitablecomposition of the casting layer 34 is PET having a thickness, forexample, of about 12 microns. A particularly preferred thickness of thecasting layer is less than 20 microns and, in particular, in a range of5-15 microns.

Referring to FIG. 4 c, as an illustration of one of the many variationsthat are possible in the present invention, the stacked display filmdoes not require insulating layers because the polymer matrix in theliquid crystal layer is sufficiently electrically insulating to preventshorts between the electrode layers. The display film also lacks a lightabsorbing layer because the layers below the liquid crystal layerincluding the substrate are not reflective or are sufficiently lightabsorbing. The display film includes the optional preparation layer 34,not the adhesive layer 32. The adhesive layer is laminated onto thesubstrate and could have adhesive properties on one or both sides.

The cured stacked display film is lifted from the release liner (notshown). The stacked display film is then transferred onto the substrate30. In particular, the optional preparation layer (or casting layer ifno preparation layer is used) bonds to the adhesive layer.

Referring to FIG. 5, another embodiment of the invention is directed toa monochrome reflective transfer display film that is transferred onto aclear substrate such as a transparent polymer or glass. In this case,the transfer film does not include a dyed or light absorbing layer. The“lower” conductor (at the time of transferring the display film to thesubstrate) is either a transparent conductor or may not be part of thetransfer film if the lower conductor is on the substrate. The upperconductor in the sequence in which the stacked layers are transferred tothe substrate may be an opaque conductor in which case the clear coat isreplaced by a black coat. Thus, during fabrication of the transferdisplay film, either the lower or the upper part of the film in relationto the release liner can be ultimately near the top or bottom of theoperational display after transfer to the substrate. In addition, thetop and bottom of the stacked display film can be either clear oropaque. It will be appreciated that terms such as upper, lower, outerand the like are used to assist in describing features of the invention.These terms are relative and change with the orientation of the display,the display film and the layers of the display film and thus, theseterms should not be used to limit the present invention.

In particular, the display film 40 is fabricated by laminating orcasting each of the layers on a surface that can serve as the releaseliner 12 in the following sequence. An optional adhesion layer 42 isfirst coated or laminated onto the release liner 12. An optional castinglayer 44 is laminated onto the adhesion layer. A conductive electrodelayer 46 (that will be the upper electrode layer in the finisheddisplay) is then coated or printed and suitably patterned on theunderlying layer. In this embodiment, the conducting material istransparent. Carbon based materials and conducting polymers are suitableas long at they provide sufficient conductivity; for example, less than1000 Ohms/square resistivity, a parameter also controlled by thethickness of the layer. Conducting polymers and carbon based materialsmight be suitable in that, often they can be printed to form a desiredelectrode pattern.

An optional electrical insulation layer 48 printed or coated over theelectrode layer 46 is advantageous in preventing electrical shorting.However, if the cholesteric liquid crystal is dispersed in a binder orpolymer matrix that is itself sufficiently electrically insulating, theinsulation layer may be omitted. The insulation layer is preferably lessthan 1.0 micron thick in order to maintain suitable drive voltages.

The cholesteric liquid crystal layer 50, which is in the form of adispersion composed of liquid crystal dispersed in a polymer matrix, isthen coated over the insulation layer. The liquid crystal dispersionmaterial can be made from any of several different processes such asemulsion or microencapsulation processes.

A second optional electrical insulation layer 52 may be advantageous inpreventing electrical shorts.

A transparent or nonreflective conductive layer is then printed orcoated and suitably patterned to serve as the conductive electrode layer54 (that will be the lower electrode layer of the finished display).Transparent conducting polymers or carbon nanotube materials aresuitable for this purpose. The transparency-to-conductivity ratiodepends on the thickness of the coating. If response speed of thedisplay is not an issue, a resistivity as high as a few thousandOhms/square is suitable.

An optional light absorbing layer 56 is printed or coated onto theelectrode layer and will be located near the bottom of the finisheddisplay.

Finally, an optional protective coating 58 is printed or coated onto thelight absorbing layer to ruggedize the display. This layer forms thebottom of the finished display, which can be mounted to a housing of thedisplay device.

The display film is cured. Then, as shown in FIG. 6 a the cured displayfilm is lifted from the release liner 12. As shown in FIG. 6 b, thedisplay film is then transferred or laminated onto the back side of atransparent substrate 30. The adhesive layer adheres the display film tothe substrate with a desired level of adhesiveness.

An embodiment of the invention laminates the transfer film “upsidedown,” i.e., with the side of the uppermost protective layer on thestacked display film relative to the release liner, being transferred soas to be adjacent to the substrate. In this embodiment the uppermostprotective layer of the stacked display film is replaced with apreparation coat that may itself function as an adhesive or as a layerthat is effective to bind to an adhesive layer.

If the intended substrate is a bottom substrate that is not transparent,it may be desirable that the preparation layer is dyed to absorb lightover some spectral band width and that the light absorbing layer(commonly added as one of the first layers during fabrication of thestacked display film) is removed. Furthermore, the lower conductingelectrode as well as the layers adjacent the release liner would betransparent. If the substrate is intended to form an upper transparentsubstrate of the display device, the light absorbing layer would becoated as one of the first layers in the fabrication process asdescribed in more detail below.

More specifically, referring to FIG. 7, the display film 60 includes anoptional casting layer 62 printed or coated on the release liner 12. Inthis embodiment, the display film is flipped 180° in the process oftransfer onto the substrate as described below. The casting layer may betransparent or need only be nonreflective depending on whether thesubstrate is an upper or lower substrate of the display device. Next, anoptional light absorbing layer 64 is printed or coated. This lightabsorbing layer 64 would not be used when the display film istransferred onto a substrate 30 b, 30 c that is intended to form thebottom portion of the display device (FIGS. 9 b, 9 c). However, when thesubstrate 30 d is intended to form a top portion of the display device(FIG. 9 a), the light absorbing layer 64 would be used in the positionshown.

Next, the conductive electrode layer 66 is printed, coated and suitablypatterned onto the underlying layer. Upon transfer onto a transparentupper substrate 30 d (FIG. 9 a), the electrode layer 66 will be locatedas a lower electrode of the display device. In this case, the electrodelayer need not be transparent but should be non-reflective. Upontransfer of the stacked display film to a bottom substrate 30 b, 30 c(FIGS. 9 b, 9 c), the electrode layer 66 is an upper electrode andshould be transparent. An optional insulating layer 68 is printed orcoated onto the underlying layer. Next, the cholesteric liquid crystaldispersion layer 70 is coated or printed onto an underlying layer of thestacked layers. An optional insulation layer 72 is printed or coatedonto the liquid crystal layer.

Next, an electrically conductive electrode layer 74 is printed or coatedand suitably patterned onto the underlying layer. If the intendedsubstrate is a transparent upper substrate 30 d (FIG. 9 a), theelectrode layer 74 is an upper electrode layer and should betransparent. If the intended substrate is a lower substrate 30 b, 30 c(FIGS. 9 b, 9 c), the electrode layer 74 is a lower electrode layer andneed not be transparent but should be nonreflective.

Next, an optional light absorbing layer 76 is printed or coated onto theelectrode layer 74. If the intended substrate is a clear upper substrate30 d (FIG. 9 a), no light absorbing layer 76 would be printed or coatedonto the electrode layer at this location. If the intended substrate isa clear or insufficiently light absorbing, bottom substrate 30 c (FIG. 9c) then the light absorbing layer 76 is used. If the intended substrate30 b is opaque and sufficiently light absorbing, the light absorbinglayer 76 may be omitted. However, if improved contrast is desired, thelight absorbing layer may be used even with opaque bottom substrate 30 b(FIG. 9 b). It should also be apparent to those skilled in the art thatlight absorbing layers may not only absorb all or some light of certainwavelengths but may also be designed to reflect different colors in thisand any other embodiment of the present invention.

The next layer is an optional preparation or protective layer 78. Thisis followed by an optional adhesive layer 80. As shown in FIGS. 9 a-c,the adhesive layer may directly bond to the substrate. The optionalpreparation layer may interact with or hold the adhesive layer to therest of the stacked display film or provide other functions such asrefractive index matching or to protect or ruggedize the display filmand possibly act as an isolation layer to protect the dispersion frommolecules in the adhesive.

In another aspect of the invention, an adhesive layer 81 could beapplied to the substrate (FIG. 9 d), in which case the adhesive layer 80would not be needed on the stacked display film. The preparation orprotective layer 78 of the display film would then be bonded to thesubstrate via the substrate adhesive layer 81. In the case where nopreparation or protective layer 78 is used, the next layer of thestacked display film would be bound to the substrate adhesive layer 81.

In the case of transfer of the stacked display film to a transparentupper substrate (FIG. 9 a), the preparation/protective and adhesivelayers should be transparent. If the stacked display film is transferredto a lower substrate, the preparation/protective and adhesive layersneed not be transparent but should not be reflective (FIGS. 9 b and 9c).

Another embodiment of the invention is directed to a monochromecholesteric reflective display that possesses full reflectivebrightness, reflecting more than 50% of incident light. In thisembodiment, the liquid crystal dispersion layer is made up of twostacked coatings, one of a left hand twist cholesteric liquid crystaland the other of right hand twist cholesteric liquid crystal, both tunedto the same pre-selected peak wavelength of reflection and bandwidth.Stacked layers of cholesterics of opposite handedness reflect bothcomponents of circular polarized light and as such can, theoretically,reflect all incident light at the Bragg wavelength of the films.Practically, some light is lost to scattering for defects in thedispersion and unwanted reflections and absorptions from the otherlayers in the stack. The total reflection can approach 80% of incidentlight as indicated in U.S. Pat. No. 6,320,563. Instead of two stackedlayers, left and right handed microencapsulated droplets may be cast asone coating.

More specifically, the display film includes an optional adhesive layer82 printed or coated on the release liner 12 and an optional preparationlayer 84 printed or coated on the adhesive layer as illustrated in FIG.10. An optional casting layer 86 is printed or coated on the underlyinglayer. An optional light absorbing layer 88 is printed or coated on thecasting layer. The light absorbing layer is used if the display film ismounted onto a substrate that is not sufficiently light absorbing inthis display that is viewed from the side that is distal to thesubstrate. Next, an electrode layer 90 is printed or coated and suitablypatterned onto the underlying layer. This is followed by an optionalelectrically insulating layer 92.

The cholesteric liquid crystal dispersion layer 94 is printed or coatednext. This is composed or two sublayers: sublayer 94 a having a right orleft hand twist sense and sublayer 94 b having the opposite twist sense.An optional barrier layer 95 is coated in between to isolate the twosublayers. This provides the display with optimized brightness becauseboth left and right hand circularly polarized light is reflected fromthe cholesteric layer 94. The pitch length of each liquid crystal layercan be tuned to reflect light at the same wavelength of peak reflection,creating a monochrome display.

Next, an optional electrically insulating layer 96 is printed or coatedon the liquid crystal layer. An electrode layer 98 is printed or coatedand suitably patterned onto the underlying layer. Next, an optionalprotective layer 100 is printed or coated onto the electrode layer.

As shown in FIG. 11 a, the cured display film is lifted from the releaseliner 12. The display film is transferred onto the substrate 30 as shownin FIG. 11 b. The adhesive layer 82 bonds to the substrate, retainingthe display film on the substrate.

The display shown in FIG. 10 a is the same as in FIG. 10 except thatrather than using two LC sublayers of right and left handed twist senseand an optional barrier layer between them, the display uses a single LClayer 93 in which LC droplets of right and left handed twist sense aredispersed.

A full-color, single reflective dispersion layer is possible if thedroplet dispersion layer is patterned with red (R), green (G) and blue(B) pixels within a single layer for additive color mixing (FIGS. 12, 13a, 13 b). The film is similar to the display film of FIG. 10, exceptthat the droplet dispersion has been patterned by a process such as UVirradiation of cholesteric material with a UV sensitive twisting poweras disclosed in U.S. Pat. No. 5,668,614, which is incorporated herein byreference in its entirety.

Another embodiment of the invention is a full color display film 110fabricated using a three layer RGB (red, green, blue) stack with asingle conducting electrode layer in between each layer (FIGS. 14, 15 a15 b). Such a display is addressed by a shared electrode addressingscheme possible with bistable cholesteric dispersions, as disclosed inthe U.S. patent application entitled “Stacked Display with SharedElectrode Addressing,” PCT/US05/03141.

In particular, an optional adhesive layer 112 is printed or coated ontothe release liner 12. This is followed by printing or coating of anoptional preparation layer 114. An optional casting layer 116 is thenprinted or coated onto the underlying layer. Next, an optional lightabsorbing layer 118 may be printed or coated. An electrode layer 120 isprinted or coated and suitably patterned next onto the underlying layer.This is followed by an optional electrical insulation layer 122.

Next, a first cholesteric liquid crystal dispersion layer 124 is printedor coated, reflecting one of the primary colors, e.g., red. A firstelectrode layer 126, which is sandwiched between optional electricalinsulation layers 128, 130, is printed or coated and suitably patternednext. This is followed by printing or coating a second cholestericliquid crystal dispersion layer 132 reflecting a second primary color,e.g., green. A second electrode layer 134, which is sandwiched betweenoptional electrical insulation layers 136, 138, is printed or coated andsuitably patterned next. A third cholesteric liquid crystal dispersionlayer 140 reflecting the third primary color, e.g., blue, is printed orcoated next. This is followed by an optional electrical insulation layer142. A third electrode layer 144 is printed or coated and suitablypatterned next. An optional protective layer 146 is added to ruggedizethe display. It will be appreciated by those skilled in the art that allof the layers upstream of the first liquid crystal layer in thedirection of incident light, should be transparent and that the layersdownstream of the first liquid crystal layer need not be transparent butshould be non-reflective. Suitable modifications to the particulardisplay shown can be made as would be apparent to one skilled in the artin view of this disclosure, such as to design the display film fortransfer onto a clear upper substrate and to invert the display 110after curing on the release liner during transfer to the substrate.

Added brightness may be achieved if each of the R, G and B layerscontains a left twist and a stacked right twist sublayer (FIGS. 16, 17a, 17 b). This display is similar to that shown in FIGS. 14, 15 a, 15 b.The difference in this display is that each of the liquid crystal layersis comprised of sublayers each having a different twist sense than theother sublayer but reflecting light at the same peak reflection andbandwidth as the other sublayer. Liquid crystal layer 125 is composed ofsublayers 125 a, 125 b; liquid crystal layer 133 is composed ofsublayers 133 a, 133 b; liquid crystal layer 141 is composed ofsublayers 141 a, 141 b. Optional barrier layers 127, 135 and 143 aredisposed between sublayers. This provides the display with optimizedbrightness.

The display shown in FIG. 16 a is the same as in FIG. 16 except thatrather than two LC sublayers of right and left handed twist sense and anoptional barrier layer between them, the display uses a single LC layer129, 137, 145 in which the LC droplets of right and left handed twistsense are dispersed and no such barrier layer.

Yet another embodiment of the invention features an infrared reflectivedisplay containing at least one droplet dispersion layer of the stackthat reflects in the infrared such as might be used for night visionpurposes (FIGS. 18, 19 a, 19 b) as disclosed in U.S. Pat. No. 6,034,752.More specifically, an optional adhesive layer 150 followed by anoptional preparation layer 152 are printed or coated onto the releaseliner. Next, an optional casting layer 154 is printed or coated onto theunderlying layer. An optional light absorbing layer 156 is printed orcoated onto the casting layer. An electrode layer 158 is printed orcoated and suitably patterned next. Onto this is printed or coated anoptional electrical insulation layer 160. Next is printed or coated acholesteric liquid crystal dispersion layer 162 having a pitch lengtheffective to reflect infrared electromagnetic radiation. An intermediateelectrode layer 164, which is sandwiched between optional electricalinsulation layers 166, 168, is printed or coated and suitably patternedonto the underlying layer. Another cholesteric liquid crystal dispersionlayer 170 is disposed next, having a pitch length effective to reflectvisible light. An optional electrical insulating layer 172 is printed orcoated next. An electrode layer 174 is printed or coated and suitablypatterned next. Finally, an optional protective coating 176 forms anouter surface of the display film.

A self-powered display may be achieved by laminating the transferdisplay film onto a solar panel as the substrate 30 (or on a substrateon which a solar panel is mounted), whereby light that is not reflectedby the cholesteric material can be absorbed in the solar panel forconversion into electrical power for powering the display. One suchtransfer film could be that of FIG. 1 (display film 10) where the lightabsorbing layer 16 is eliminated, so that light can be absorbed in thesolar panel and used to power the display.

Another display film is mounted onto an active matrix backplane as shownin FIGS. 20, 21 a, 21 b. The optional casting layer 182 is printed orcoated onto the release liner 12. An optional electrically insulatinglayer 186, which may also serve as a casting layer, is printed or coatedonto the release liner 12. The next layer is a cholesteric liquidcrystal dispersion layer 188. The dispersion layer may also serve as thecasting layer. An optional electrical insulation layer 190 is printed orcoated next. Finally, an unpatterned protective/electrically conductivelayer 192 is printed or coated onto the underlying layer.

The cured display film is lifted from the release liner (FIG. 21 a). Thedisplay film is then transferred onto a substrate 30 containing anactive matrix backplane 194 (FIG. 21 b), which can electrically addressindividual pixels of the display.

FIGS. 22, 23 a, 23 b show an embodiment of the invention in which someof the display components are located on the substrate. The display film200 includes an optically transparent casting layer 202 printed orcoated onto the release liner. An optically transparent conducting layer204 is printed or coated and suitably patterned onto the casting layer.Next, a cholesteric liquid crystal dispersion layer 206 is printed orcoated. Then, an optional adhesion layer 208, which may also serve as anelectrical insulating layer, is printed or coated onto the liquidcrystal layer. As illustrated in FIG. 23 a, the film is lifted off ofthe release liner and flipped 180 degrees during transfer. Asillustrated in FIG. 23 b, the film is laminated onto the substratecontaining a printed or coated and suitably patterned conductor layer214 such that the side of the transfer film containing the adhesionlayer 208 (shown at an upper portion of the stack in FIG. 22) isadjacent to the conductor 214 on the substrate (shown at a lower portionof the stack in FIG. 23 b). If the optional adhesion layer 216 isapplied to the substrate, the adhesion layer 208 of the stacked displayfilm may not be needed and vice versa. The electrode layer 204 of themulti-layer stack and the electrode layer 214 on the substrate sandwichthe liquid crystal dispersion layer 206 therebetween and together form acompleted display. The layer 202 serves not only as a casting layerduring printing or coating the layers on the release liner, but also asa transparent outer protective layer once the display film has beenlaminated onto the substrate.

Another embodiment of the present invention is directed to the use offlexible substrates. FIG. 24 shows a display film 220 adapted for use ona fabric substrate. An optional adhesive layer 222 is printed or coatedonto the release liner 12. An optional preparation layer 224 is printedor coated onto the underlying layer. An optional casting layer 226 isprinted or coated onto the underlying layer or, if none, onto therelease liner 12. An optional electrode layer 228 is printed or coatedand suitably patterned next. In the case of application of the displayfilm to a substrate that is sufficiently light absorbing, no lightabsorbing layer may be used. However, it should be apparent that a lightabsorbing layer could be added below the liquid crystal layer if thesubstrate is not sufficiently absorptive of light. An optionalelectrical insulation layer 230 is printed or coated next. Next, thecholesteric liquid crystal dispersion layer 232 is printed or coated onthe underlying layer. Next, an optional electrical insulation layer 234is printed or coated onto the liquid crystal layer. Then, an electrodelayer 236 is printed or coated and suitably patterned onto theunderlying layer. This is followed by printing or coating an optionalprotective layer 238 to ruggedize the display.

One suitable flexible substrate is in the form of a fabric 30 f. On thefabric, an optional planarization layer 240 may be disposed. This layercould include patterned electrodes in which case the electrode layer 228would be omitted. Although it is not necessary for the fabric to besmooth for lamination of the display film onto the fabric substrate, ifused, the planarization layer smooths the surface of a rough fabricsubstrate, in preparation of attachment of the transfer display film220. The cured display film is lifted from the release liner (FIG. 25a). The display film is then transferred directly onto the fabricsubstrate 30 f (FIG. 25 b), or optionally onto the substrate made flatby the planarization layer. It will be appreciated that instead of theadhesive layer disposed on the display film, the adhesive layer could bedisposed on the planarization layer (not shown).

Another embodiment features an optically addressable transfer displayfilm to provide a display that can be optically addressed as disclosedin the publication “Reflective Display with Photoconductive Layer andBistable Reflective Cholesteric Mixture” Journal of the SID, Vol. 5/3,pages 269-274 (1997) by Yoshida et al. This film eliminates the lowerelectrode and is transferred to a photoconductive sheet having anelectrode underneath. While a continuous voltage is applied to theelectrodes, light impinging on the display film will locally alter theresistivity of the photoconductor and drive the display film. Thedisplay can be addressed with an image suitably focused or projected onthe film, or written with a scanned laser beam.

Transfer display films formed from other veneered stacks are possibledepending on the desired application and fall within the scope of thepresent invention. For example, when sequences of display elements arelisted, it will be apparent that the invention contemplates otherelements interposed between the listed elements. In addition, whetherthe display film is placed on a light absorbing substrate or not affectsthe selection of the light absorbing layer in the multilayer stack. Forexample, laminating the display onto a transparent upper substrate,affects selection of whether and where a light absorbing layer will beused and affects selection of transparent or opaque conductors. Inaddition, variation in the invention is enabled by the use of anadhesive layer, preparation or protective layers. One or more of theselayers may be disposed on the substrate, for example, a preparationlayer on the multilayer film and the adhesive layer disposed on thesubstrate. The multilayer stack may include one, two or more electrodelayers. If the substrate already has an electrode layer disposed on it,one less electrode layer may be formed in the multilayer stack. Transferonto the substrate sandwiches the liquid crystal layer between theelectrode layer in the display film and the electrode layer on thesubstrate. Also, in the case of other devices for applying a voltage tothe liquid crystal layer, such as the active matrix backplane or devicefor optically addressing, the multilayer stack may omit an electrodelayer. Finally, layers may have multi-functionality such as anelectrode/planarization layer, a planarization/electrical insulationlayer, an electrode/casting layer, an electrode/casting/protectivelayer, for example. Those skilled in the art in view of this disclosurewill appreciate these and other variations to layer multi-functionality,layer and substrate type, to the sequence of the layers and to theorientation of the display film, which fall within the scope of thepresent invention. Accordingly, it will be apparent to those skilled inthe art that the novel fabrication process of the present inventionprovides a myriad of variations in the design and use of the inventivedisplay film, all without departing from the spirit and scope of thepresent invention.

FIG. 26 is a perspective drawing of a passive matrix display 300illustrating, in an exploded view, how the conducting transparentelectrodes 302 patterned as rows, may be electrically connected toconducting tabs 304 attached to the substrate 306. The column electrodes308 are electrically connected to tabs 310, which are also attached tothe substrate. The tabs are used for interconnecting drive electronics,not shown. Since the tabs for both of the columns 308 and rows 302 aredisposed on the substrate, attaching the drive electronics is greatlysimplified. It will be apparent that the intermediate layers of thedisplay, including the cholesteric liquid crystal dispersion layer, arenot shown in FIG. 26 for clarity.

In the case where there are multiple electrode layers, such as that of afull-color display with an RGB stack of three cholesteric liquid crystaldispersion layers, the column and row electrodes can likewise beconnected to tabs located on the substrate. For example, the two outerconducting layers in the full-color stacked substrate can be connectedto tabs located on two sides of the substrate as illustrated in FIG. 8of the U.S. patent application entitled “Stacked Display with SharedElectrode Addressing,”, while the two intermediate electrode layersassociated with the full color stack can be connected to tabs located onthe two remaining sides of the substrate. Electrical connections of theelectrodes to the tabs can be made with conducting polymer material. Theends of the electrodes of the conducting layers are left exposed in thecoating process to allow for connection to the tabs.

Particular aspects of the invention will now be described by referenceto the following examples that are provided to improve understanding ofthe invention and should not be construed to limit the scope of thepresent invention as set forth in the appended claims.

EXAMPLE 1

An operable 16×16 pixel passive matrix, lift-off cholesteric displayfilm was made by first coating and printing the various display elementson a release liner to form a display film, then lifting the film off ofthe liner for subsequent lamination on a substrate. The release linerwas a neoprene sheet with a fabric support available from Thor Labs(Newton, N.J.). A casting layer of aqueous polyurethane dispersion,WITCOBOND W232 (available from Crompton Corporation, CT) was depositedon the release liner using a Meyer rod technique and allowed to dry atroom temperature. The dry thickness of the casting layer wasapproximately 10-12 microns. A layer of conductive polymer (ELP-3040available from Agfa-Gevaert, Belgium) was screen printed on the castinglayer as 5 mm wide, 15 cm long strips spaced 1 mm apart to serve as thecolumn electrodes of the passive matrix display. After casting, theconducting polymer was cured at 100° C. for 10 minutes. A thininsulation layer (1-2 μm) of polyurethane dispersion (e.g. WITCOBONDW232) was cast on the conductive layer using a doctor blade technique. Alayer of encapsulated cholesteric liquid crystal in polymer binder wascoated from a water-based emulsion on the insulation layer using adoctor blade having a 25 micron gap and allowed to dry for 1 hour atroom temperature. The thickness of the encapsulated liquid crystal layerwas approximately 8-10 μm. The ratio between liquid crystal and binderwas from 4:1 to 5:1. The emulsion was prepared from 0.4 g of ChLC KLC19(EM Industries, Hawthorne, N.Y.) and 0.27 g of NeoRez R967 availablefrom NeoResins, MA were emulsified with a homogenizer (PowrerGen 700) at1000 rpm for 3-4 minutes at room temperature. The emulsified ChLC formeddroplets that were about 3-25 μm in diameter. After the emulsion layerdries at room temperature for 1 hour the droplet shape appeared to beflattened. Such droplet shape reduces light scattering and enhances thedisplay brightness. A second conductive electrode was a highlytransparent conductive polymer Dipcoat available from Agfa. A thin layerof conductive polymer was deposited using air brushing over a mask andcured at room temperature. The mask was patterned to provide 5 mm wide,15 cm long strips spaced 1 mm apart to form the row electrodes of thepassive matrix display. For protection of the display, a 5-10 micronclear coat was deposited on the top of the second conductive electrodeusing a doctor blade. Moreover, the use of the clear coat layer made ofthe polyurethane dispersion (e.g. WITCOBOND W232 or NeoRezR967) resultedin an increase in the transmission due to the refractive index matching.

The display film including all of the layers from the casting layer tothe clear coat was lifted off from the release liner. The thickness ofthe lift-off display was around 30 microns. The lift-off display filmwas fully operational upon being electrically addressed by applying theappropriate voltages to the column and row electrodes. The bistablecholesteric material could be addressed to the planar (yellowreflective) by application of 135 volts or to the focal conic(non-reflective texture) with application of 105 volts. The appropriatevoltages used to achieve the planar and focal conic states are dependenton the compositions and thicknesses of the layers of the display.Suitable such voltages may be selected by one of ordinary skill in theart in view of this disclosure based on the particular characteristicsof the display layers. Pixels addressed to the planar and focal textureremained in their respective states even when the film was bent,twisted, folded, and even stretched. The display film had a contrastratio of 12:1 and a brightness of 28%. The display film was very ruggedand suitable for lamination on a substrate without damage. In thisparticular example, it is desired that the substrate be opaque andpreferably black so that the focal conic state appears black and thereflective planar state appears a bright yellow and highly contrastingagainst the black.

EXAMPLE 2

An operable 16×16 pixel passive matrix, lift-off cholesteric displayfilm was made by first coating and printing the various display elementson a release liner to form a display film, then lifting the film off ofthe liner for subsequent lamination on a substrate. The sequence of thelayers was the same as in the Example 1 except that the insulation layerwas made of polyurethane dispersion NeoRez R967.

EXAMPLE 3

An operable 16×16 pixel passive matrix, lift-off cholesteric displayfilm was made by first coating and printing the various display elementson a release liner to form a display film, then lifting the film off ofthe liner for subsequent lamination on a substrate. The sequence of thelayers was the same as in the Example 1 except that the casting layerwas made of polyurethane dispersion NeoRez R967 and it did not have theinsulation layer between the first conductive electrode and the layer ofencapsulated liquid crystal.

EXAMPLE 4

The following is an example of preparation of the stacked layers ofmaterials for a lift-off display film with adhesive and casting layers.An operable 4×1 pixel passive matrix cholesteric display lift-off filmwas made by first coating and printing the various display elements on arelease liner to form a display film, then lifting the film off of theliner forming the lift-off film for subsequent lamination on a fabricsubstrate. The release liner was the same as in Example 1. The castinglayer was a 12.5 micron polycarbonate plastic sheet laminated with apressure sensitive adhesive layer. The sequence of the layers is similarto that in the Example 1 with the exception of the casting and adhesionlayers. Following the coating and drying of the layers the display filmfrom the adhesion layer to the clear protective coat was lifted off fromthe release liner and laminated onto black soft cloth. The display wasfully operational after transfer to the final substrate. The bistablecholesteric material was addressed to the planar (yellow reflective) byapplication of 110 volts or to the focal conic with application of 55volts. The display film had a contrast ratio of 12:1 and a brightness of30%.

EXAMPLE 5

The following is an example of preparation of the stacked layers ofmaterials for a lift-off display with an adhesive and casting layer. Thedisplay had the same sequence of layers as in Example 1 except that therelease liner was a paper sheet with a peel-off adhesive transparentlayer that served as a casting layer (Avery laminating sheets 73602). Toestablish a black background for the reflective display a black paint(KRYLON) was coated on the casting layer by spraying and dried at roomtemperature. A 2×2 pixel display was prepared as follows. First, a layerof conductive polymer (ELP3040) was deposited with Meyer rod on theblack paint and cured at 80° C. for 15 minutes. Next, a layer ofencapsulated liquid crystal and second conductive electrode weredeposited the same way as described in Example 1. The display did nothave a clear coat layer as a top layer. The display film had a contrastratio of 18:1 and brightness of 34%. The driving voltage was 95 V forachieving the planar state and 60 V for achieving the focal conic state.

EXAMPLE 6

An operable 1×7 pixel passive matrix cholesteric display with twoelectro-active layers was made by coating and printing the variousdisplay elements on a release liner to form a display film, then liftingthe film off of the liner for subsequent lamination on a substrate. Therelease liner with casting layer, patterned conductive polymer layer,encapsulated ChLC layer and the second conductive electrode were thesame as in Example 1 except that the second conductive electrode was notpatterned and was deposited over a mask which provides a solidelectrode. No clear coat layer was deposited on the second transparentelectrode. Instead, a thin isolation layer coated from aqueous gelatinsolution (HiPure gelatin, Norland Products) was deposited with a doctorblade. A second layer of yellow encapsulated ChLC in polyurethane binder(NeoRes R967) was coated from a water-based emulsion on the isolationlayer with doctor blade. The thickness of the second encapsulated ChLClayer was approximately 8-10 μm. A third conductive transparentelectrode made of conductive polymer Dipcoat was deposited over a maskusing air brushing and cured at room temperature. The mask provides apatterned electrode of the passive matrix display. Finally, the topclear coat as in Example 1 was coated on the third conductive electrode.Each encapsulated ChLC layer can be addressed separately.

EXAMPLE 7

An operable 1×7 pixel passive matrix cholesteric display with twoelectro-active layers was made by coating and printing the variousdisplay elements on a release liner to form a display film, then liftingthe film off of the liner for subsequent lamination on a substrate. Thesequence of the layers is the same as in the Example 6 except that thereis no isolation layer between the second conductive electrode and thesecond ChLC layer. The color of the first ChLC layer was red and thecolor of the second ChLC layer was green. In this Example the secondChLC layer consisted of two sub-layers. The first sub-layer was anisolation layer and was coated from an aqueous emulsion of greenmicroencapsulated ChLC on the second conductive electrode using thedoctor blade. Microencapsulated ChLC droplets with sizes ranging from2-20 microns had individual shells made of cross-linked gelatin and gumArabic using complex coacervation process (LCR, Ml). The purpose of thissub-layer was two-fold. It served as an isolation layer to preventmixing of red and green ChLCs, and being electro-active improved thedroplet fill factor and increased the display brightness. The secondsub-layer was a major electro-optical layer of the green encapsulatedChLC, and was deposited from aqueous emulsion as in Example 6.

EXAMPLE 8

An operable 16×16 pixel passive matrix cholesteric display with twoelectro-active layers was made by coating and printing the variousdisplay elements on a release liner to form a display film, then liftingthe film off of the liner for subsequent lamination on a substrate. Thesequence of the layers is the same as in the Example 7 except that thefirst and third conductive electrodes were patterned to form rows andcolumns as in Example 1.

EXAMPLE 9

An operable 1×7 pixel passive matrix cholesteric display with oneelectro-active layer was made by coating and printing the variousdisplay elements on a release liner to form a display film, then liftingthe film off of the liner for subsequent lamination on a substrate. Thesequence of the material layers is the same as in the Example 3 exceptthat the casting layer was made of 0.5 mil clear PET film with opticalpressure sensitive adhesive (PSA) layer on a release liner (from GrafixPlastic, Cleveland, Ohio). The display film including all of the layersfrom the casting layer with PSA layer to the clear coat was lifted offfrom the release liner and laminated on the fabric substrate. Thedisplay film had a brightness of 32%. The driving voltage was 110 V forthe planar state and 55 V for the focal conic state.

EXAMPLE 10

The sequence of the materials layers is the same as in the Example 9except that the casting layer was made of 1 mil LB grade clear acetatefilm (from Grafix Plastic, Cleveland, Ohio). The display film had abrightness of 31%. The driving voltage was 120 V for the planar stateand 60 V for the focal conic state.

Many modifications and variations of the invention will be apparent tothose of ordinary skill in the art in light of the foregoing disclosure.Therefore, it is to be understood that, within the scope of the appendedclaims, the invention can be practiced otherwise than has beenspecifically shown and described.

1. A transfer display film comprised of stacked layers that are preparedon, cured or dried and lifted from a release surface and thentransferred to a substrate, wherein said stacked layers comprise atleast one liquid crystal dispersion layer comprising liquid crystalmaterial dispersed in polymer, a first electrically conductive layerlocated near one side of said dispersion layer, a second electricallyconductive layer located near the other side of said dispersion layerand an electrical insulation layer located between and in contact withsaid dispersion layer and said first or second conductive layer.
 2. Atransfer display film according to claim 1 comprising a casting layerapplied on or near the release surface on which other said layers of thedisplay are prepared.
 3. A transfer display film according to claim 1wherein said plurality of stacked layers are stacked in a sequencecomprising a casting layer, said first said electrically conductivelayer, said dispersion layer, and said second said electricallyconductive layer.
 4. A transfer display film according to claim 3wherein at least one of said first and second electrically conductinglayers comprises a transparent electrical conductor formed of aconducting polymer or carbon nanotube material.
 5. A transfer displayfilm according to claim 3 wherein said dispersion layer comprises atleast one of an emulsion, phase separation and microencapsulated liquidcrystal material.
 6. A transfer display film according to claim 3comprising a light absorbing layer located between said casting layerand said dispersion layer.
 7. A transfer display film according to claim3 comprising a clear protective layer located over the secondelectrically conducting layer to ruggedize said transfer display film.8. A liquid crystal display comprising the transfer display filmaccording to claim 7 further comprising said substrate attached to saidtransfer display film near said casting layer.
 9. A transfer displayfilm according to claim 3 comprising a protective layer coated over saidsecond electrically conductive layer as an upper conducting electrode,wherein said protective layer is optically opaque and said layers aretransferred to a transparent said substrate with said casting layernearest to said substrate to operate as a reflective display.
 10. Atransfer display film according to claim 3 comprising a protective layercoated over said second electrically conductive layer as an upperconducting electrode, wherein said protective layer is optically clearand said film is transferred to said substrate with said casting layernearest said substrate to operate as a reflective display, wherein saidcasting layer is coated, printed or laminated over an adhesive layerthat lifts off said release surface with said casting layer.
 11. Atransfer display film according to claim 1 wherein said liquid crystalcomprises bistable cholesteric liquid crystal.
 12. A transfer displayfilm according to claim 1 comprising an outer adhesive layer.
 13. Atransfer display film according to claim 1 wherein the at least one saiddispersion layer comprises at least one bistable cholesteric liquidcrystal reflective of visible or infrared electromagnetic radiation. 14.A transfer display film according to claim 13 comprising a transparentelectrically conductive layer located between adjacent said dispersionlayers.
 15. A transfer display film according to claim 13 wherein the atleast one said dispersion layer comprises one said dispersion layerreflective of red light, another said dispersion layer reflective ofblue light and another said dispersion layer reflective of green lightand electrically conductive layers are disposed between said dispersionlayers.
 16. A transfer display film according to claim 1 wherein saiddispersion layer comprises left and right hand twist cholestericmaterials, separated to prevent mixing.
 17. A transfer display filmaccording to claim 16 wherein said dispersion layer comprises onesublayer including said left hand twist cholesteric material and anothersublayer comprising said right hand twist cholesteric material.
 18. Atransfer display film according to claim 1 wherein said dispersion layeris patterned with red, green and blue pixels.
 19. A liquid crystaldisplay device comprising the transfer display film and said substrateof claim 1 and driving circuitry connected to said electricallyconductive layers.
 20. A liquid crystal display device according toclaim 19 wherein said substrate is a solar panel effective to provide aself-powering display.
 21. A liquid crystal display device according toclaim 19 wherein said substrate comprises a photoconductive sheet andsaid first electrically conductive layer adapted to enable said liquidcrystal layer to be driven by impinging light onto said display filmwhile applying voltage to said second electrically conductive layer andsaid first electrically conductive layer.
 22. A liquid crystal displaydevice according to claim 19 wherein said substrate comprises an activematrix device.
 23. A liquid crystal display device according to claim19, wherein-one of said first electrically conductive layer and saidsecond electrically conductive layer contains parallel strips of rowconductors and the other of said first electrically conductive layer-andsaid second electrically conductive layer contains parallel strips ofcolumn conductors.
 24. A transfer display film according to claim 19comprising an outer layer of adhesive.
 25. A liquid crystal displaydevice comprising the transfer display film and the substrate of claim 1, wherein said substrate comprises one of said electrically conductivelayers, further comprising driving circuitry connected to saidelectrically conductive layers.
 26. A transfer display film according toclaim 1 comprising a protective layer coated over said secondelectrically conductive layer as an upper conducting electrode, saidpreparation layer being an adhesive layer or serving to hold an adhesiveovercoat, wherein said display film is transferred to said substratewith said preparation layer adjacent said substrate to operate as areflective display.
 27. A lift-off display film comprising stackedlayers that are prepared on, cured or dried and then lifted from arelease surface, wherein said stacked layers comprise at least oneliquid crystal dispersion layer comprising liquid crystal materialdispersed in polymer, a first electrically conductive layer located nearone side of said dispersion layer, a second electrically conductivelayer located near the other side of said dispersion layer and anelectrical insulation layer disposed between and in contact with saiddispersion layer and said first or second conductive layer.
 28. Alift-off display film according to claim 27 wherein said dispersionlayer comprises at least one of an emulsion, phase separation andmicroencapsulated liquid crystal material.
 29. A lift-off display filmaccording to claim 27 wherein said liquid crystal comprises bistablecholesteric liquid crystal.
 30. A lift-off display film according toclaim 27 wherein one of said first electrically conductive layer andsaid second electrically conductive layer comprises parallel rowelectrode strips and the other of said first electrically conductivelayer and said second electrically conductive layer comprises parallelcolumn electrode strips.
 31. A lift-off display film according to claim27 comprising a clear protective layer located over at least one of saidfirst electrically conductive layer and said second electricallyconductive layer that ruggedizes said lift-off display film.
 32. Alift-off display film according to claim 27 comprising a stack of saiddispersion layers each reflective of visible or infrared electromagneticradiation.
 33. A lift-off display film according to claim 32 furthercomprising a transparent electrically conductive layer located betweenadjacent said dispersion layers.
 34. A lift-off display film accordingto claim 33 wherein said stack of layers comprises one said dispersionlayer reflective of red light, another said dispersion layer reflectiveof blue light and another said dispersion layer reflective of greenlight.
 35. A lift-off display film according to claim 27 comprising atleast one additional dispersion layer.
 36. A lift-off display filmaccording to claim 35 comprising an electrically conductive layerdisposed between dispersion layers.
 37. A display film comprising astacked sequence of layers prepared on a release liner and lifted off asa freestanding film or for transfer to a substrate, wherein each of thelayers are coated, printed or laminated on said release liner in thesequence of a casting layer, lower conducting electrode, dispersionlayer of liquid crystal dispersed in polymer, and upper conductingelectrode, said display film being operable as an electricallyaddressable display when connected to drive electronic circuitry. 38.The display film of claim 37 wherein said liquid crystal is cholestericliquid crystal.
 39. The display film of claim 37 wherein at least one ofsaid lower conducting electrode and said upper conducting electrode is atransparent conductor.
 40. The display film of claim 39 wherein the atleast one of said lower conducting electrode and said upper conductingelectrode is a conducting polymer or carbon nanotube material printed orcoated and patterned to form a desired electrode configuration.
 41. Thedisplay film of claim 37 wherein an insulation layer is coated, printedor laminated over said lower conducting electrode.
 42. The display filmof claim 37 wherein an insulation layer is coated, printed or laminatedover said upper conducting electrode.
 43. The display film of claim 37wherein an optical layer is coated over said casting layer to adjustoptical properties of said display film.
 44. The display film of claim37 wherein a protective layer is coated over said upper conductingelectrode.
 45. The display film of claim 44 wherein said protectivelayer is optically clear and said display film is transferred to saidsubstrate with said casting layer nearest to said substrate to operateas a reflective display.
 46. The display film of claim 45 wherein saidcasting layer is coated, printed or laminated over an adhesive layerthat lifts off said release liner with said casting layer.
 47. Thedisplay film of claim 45 wherein said substrate is a fabric material ofnatural or synthetic fibers.
 48. The display film of claim 44 whereinsaid protective layer is optically opaque and said display film istransferred to a transparent substrate with said casting layer nearestto said substrate to operate as a reflective display.
 49. The displayfilm of claim 37 wherein a preparation layer is coated over said upperconducting electrodes, said preparation layer being an adhesive layer orserving to hold an adhesive overcoat, said display film beingtransferred to said substrate with said preparation layer adjacent saidsubstrate to operate as a reflective display.
 50. The display film ofclaim 37 wherein said dispersion layer is a stack of sublayers ofcholesteric liquid crystal dispersions each reflective at a differentwavelength and each separated with a transparent conducting electrode.51. The display film of claim 50 wherein said stack of sublayers of saidcholesteric liquid crystal dispersions comprises one sublayer reflectivein red, another sublayer reflective in blue and another sublayerreflective in green.
 52. The display film of claim 50 wherein at leastone of said cholesteric sublayers is reflective in infrared.
 53. Thedisplay film of claim 37 wherein said dispersion layer is made up ofleft and right hand twist cholesteric materials, separated to preventmixing.
 54. The display film of claim 53 wherein said dispersion layeris a double coating, one of left and the other of right hand twistedcholesteric materials.
 55. The display film of claim 37 wherein saiddisplay film is laminated on a solar panel to provide a self-poweringdisplay.
 56. A transfer display film comprising a stacked sequence oflayers comprising at least one conducting electrode layer and acholesteric dispersion layer prepared on a release liner and lifted offfor transfer to a substrate containing a photovoltaic and a conductinglayer, said display film and said substrate together being operable asan optically addressable electronic display when connected to driveelectronic circuitry.
 57. A transfer display film comprising a stackedsequence of layers comprising at least one conducting electrode layerand a cholesteric dispersion layer prepared on a release liner andlifted off for transfer to a substrate that is an active matrixbackplane, said display film and said substrate together being operableas an actively driven electronic display when connected to driveelectronic circuitry.
 58. A transfer display film comprising a stackedsequence of layers comprising at least one conducting electrode layerand a cholesteric dispersion layer prepared on a release liner andlifted off for transfer to a substrate that contains either row orcolumn electrodes, said display film and said substrate together beingoperable as a passively driven reflective electronic display whenconnected to drive electronic circuitry.